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Full text of "Practical Wireless 1966 April"

PRACTICAL 

WIRELESS 



APRIL 1966 




^SPECIAL FEATURE ARTtCLE 







:C> 





J. 



I 



IRECT READING 



EMM 



AND REV! COUNTER 



PRACTICAL WIRELESS 



April, 1966 



SOLDERING INSTRUMENTS 
AND EQUIPMENT 




DESIGNED FOR 
THE AMATEUR'S 
RADIO STATION 



ILLUSTRATED 

List No. 70 {" BIT 

IN 
PROTECTIVE 
SHIELD 
List No. 68 



for catalogue apply direct to: — 

Sales and Service Dept. 

ADCOLA PRODUCTS LTD., 

ADCOLA HOUSE, 

GAUDEN ROAD, LONDON, S.W.4 



JACKSON 

the big name in PRECISION components 

MINIATURE TUNING CAPACITORS 

TYPE "00" 

The Jackson 'O' range 

contains six basic types 

of different air-dielectric 

tuning capacitors with a 

wide variation of capa- 
cities available in each 

type. In addition, there 

are optional extras such 

as concentric-spindle 

slow-motion drives, built- 
in trimmers and plastic 

covers. The maximum 

capacitance per section ranges from 12, 18 or 24 pr 

for FM types to 420 pF for AM types. 
•Type 00 subminiature twin capacitor at 12'6 

•Type OFM two-gang for FM at 11'- 

•Type OPC for printed circuit mounting at 14'- 
•Type OG2 with internal reduction gearing at 16'- 
MADE IN ENGLAND 

Write for literature 

JACKSON BROS. (London) LTD. 

(Dept. P.W.) KINGSWAY-WADDON, CROYDON, 
SURREY 

Phone: Croydon 2754-5 Grams: Walfilco, Souphone, 
London 




Telephones 

MACaulay 4272 & 3I0I 



Telegrams 

SOUOINT LONDON SW4 



N 0MB REX INSTRUMENTATION 

TRANSISTORISED AUDIO GENERATOR 
Model 63 £I7.I.9 

if Laboratory Specification 10 C's to 1 00 Kc/s. 
if Direct Calibration, if Sine and square output 




Also available: 



if INDUCTANCE BRIDGE 66 ... £18.6.9 

■*• POWER SUPPLY UNIT 61 ... £6.14.6 

■*• C.R. BRIDGE 62 £9.6.9 

if R.F. SIGNAL GENERATOR 27 ... £10.16.9 

All prices include Battery, Post and Packing. 

Prompt delivery 

S.A.E. for Technical Trade and Export 

Leaflets enquiries invited 

NOMBREX LTD. iw ms 

Estuary House, Camperdown Ter., Exmouth, Devon 



April, 1966 



PRACTICAL WIRELESS 



1009 



VALUE IN VALVES 



GUARANTEED 3 MONTHS 
BY ReTURN OF POST 
icttan or Money Book Guarantee on goods ii ItUimcd unwed within 

ALL VALVES ARE NEW UNLESS OTHERWISE INFORMED. 
FREE TRANSIT INSORANCE. POSTAGE 1 valve Bd. 2-11 1/-- Free over 12. 



TfTMm SATISFACTION 
#f #*#S^ GUARANTEED 



Cirr 



0Z4 

1A7GT 

1C5GT 

1H5GT 

1N5GT 

1S4 

2D21 

3A4 

3A5 

3D6 

3Q4 

3R4GY 

6C4G 

5Y30 

5Y3GT 

5Z4 

5Z4G 

5Z4GT 

6 30L2 

BA8G 

GA7G 

IIAK5 

8AQ7 

6AT6 

8A06 

8AV6 

8BA6 

8BE8 

BBG6G 

lib Hd 

6BJ6 

8BR7 

BBWB 

8BW7 

6C4 

60S 

BOB 

8C9 

urn Of; 

6D6 

8P1 

6F8Q 

BF13 

6F14 

6FX5 

6FS3 

6JMS 

BJSGT 

8J6 

8J7G 

8J7G7 

OKBGT 

6K7 

8K7G 

8K7GT 

8K8 



4/6 BKSGT 
9/6 6K.25 
7/6 6L1 
8/9 6L8 
8/9 6L6G 
7/6 6L18 
5/6 6L19 
4/- 6LD20 
6/- 6P25 
4/- 6P28 
5/- 6Q7G 
8/- 6Q7GT 
4/- 6SA7 
4/6 6SG7 
4/- 6SK7 



14/6 EBC41 
7/9 EBC81 
8/9 EBF80 
9/6 EBFSj 

18/- EBL21 



8/3 14S7 
8/6 19AQ5 
9/8 20D1 
7/3 20F2 
6/6 20L1 
7/920P1 
12/6 20P3 
7/9 20P4 17/-ECC32 
8/0.25A6G 8/- ECC34 
9/9 25L6GT 7/9 ECC40 
4/-25Z4G 7/-ECCcil 



6/3 EZ41 
5/9 EZ80 
7/6EZ81 
7/0 FC4 
8/6 GZ32 



9/- 6SX7GT 5/6 30P12 
7/- 6SN7GT 4/6 30PL1 
9/6 6SQ7 5/9 35C5 
9/- 604GT 
7/9 6V6G 
7/6 6VGT 
4/3 6X4 
5/- 6X5G 
6/- 6X5GT 
7/- 7B6 
6/- 7B7 
5/6 7C5 
5/6 7C6 
15/- 7H7 
5/-7S7 
5/-7Y4 
8/6 10C1 
6/9 10C2 
•I- 10F1 



9/6 EBL81 19/6 L.VR2 

11/- EC52 4/9 KT33C 

17/-ECC32 4/-KT86 

8/- ECC34 9/- KT44 

6/9 KT45 

4/9 KTU1 

4/9KT73 

5/9 KT66 

7/6 KT76 

6/- KT88 



7/3 80IE 
7/6 813 
5/- 86BA 
15/- 954 
4/8 855 
9/ - 956 
14/6 9001 
4/9 9002 
2/3 10LD11 14/6 9003 
5/6 10P13 8/0 ATP4 



8/- 30F5 6/- ECCS2 
5/9 30FL1 9/6 ECC33 
4/9 30L15 8/9 ECC34 
5/- 30P4 9/6 ECC85 

7/-ECC88 

9/3 EC! 80 

8/6 ECF82 
87- 35L6GT 8/- ECH21 11/6 MTJ14 
4/6 35W4 6/-ECH35 7/6 N37 
6/- 35Z4GT 5/6 ECH42 
4/6 50L6GT 8/6 ECHS1 
6/- 80 5/- ECH83 

5/6 185BT 18/6 ECL80 
9/- 185BTA19/C ECL82 
5/8 8071 A I 



5/9. R19 
5/9 SP41 
8/- SP81 
8/- T41 
7/6 TDD4 
9/- U14 
3/9 Did 

14/- I; 22 
6/- 024 
8/6 025 
8/6 026 
5/9 U35 

12/- O50 
8/6 O10? 

17/6 IJ191 



MOST MULLARD. 
9/6 MAZDA. COSSOR. 
2/3 EMITRON. EMI 
2'- SCOPE. RRIHAR. 
6/S , FERRAST1TYPES 



9/6 KTW61 5/9 0281 
6/-KTW63 5/- 0282 
S/3 KTZ63 7/- O301 



;/- 
M 
7/8 
6/9 

ie/« 

8/3 

;/- 

m 
•y- 

BM 

15/- 



PROCISSED 
OUK OWN 
FACTORY 



& Iqs. 12/6 

12in. 

15in. 

15-17in. 

19in. 

21 in. 

23in. 



6 Months 

£2. 0.0 
£2.10.0 
£3. 5.0 
£3. 5.0 
£3.15.0 
£3.15.0 



12 Months 
£3. 0.0 
£3.10.0 
£4. 5.0 
£4. 5.0 
£5.15.0 
£5.15.0 



NEW 
TYPES 

AW47-91 

£5.15.0 

AW59-91 

£7.10.0 

AW48-30 

£5.5.0 



RECORD DECKS 

I.ATEST GARRARD 
All Factory Fresh. All with cartridge. 



8/8 N78 
7/- N108 
6/3 PC86 
6/6 FC97 
'31- PCC84 



5/6 10P14 
11/- 12AH7 
17/- 12AH8 
3/-12AT6 
4/912AT7 
3/6 12AD6 
4/3 12AD7 
9/6 12AV6 
9/6 12AX7 
6/6 12BA6 
3/- 12BE6 
4/3 12BH7 
2/8 12E1 
4/912J7GT 



9/6 AZ31 
7/-B36 
9/- CBL31 
6/6CL33 
4/9CY31 
9/- DAF91 
4/9 DAF96 
6/3 DF91 
6/- DF92 
7/- DF8B 
6/6 DK9I 
8/9 DK92 
17/6 DK96 
8/- DL92 



7/612K7GT 4/- DL94 
6/- 12K8 9/9 DL96 
5/9 12K8GT 9/8 EABC80 6/- EM85 
1/-12Q7GT 5/-EAF42 3/3 EY51 
4/6 12SA7 6/3 EB41 5/- EY86 
i 12SK7 2/9 EB91 2/- EY8S 



5/-ECL83 10/0PCC85 

4/9 ECL86 10/3 PCC8S 
49/- EF3B 31- PCC89 
12/6 EF39 

3/6 EF40 

2/3 EF41 

21- EF54 

3/6 EFSO 

4/9 EF85 

5/6 EF8B 

2/6 EF89 

6/-EF91 

4/6EF92 
19/- EF183 

9/-EF184 

7/6EL32 

4/6 EX33 

7/3 EL34 

8/-EL35 

3/-EL3S 

7/3 EL41 

5/8 EL42 

7/- EL84 

7/3 EM34 

5/-EM80 

6/6EM81 
73 EM84 



SRP10 Mono (Single) Flayer {4.19.0. 
11J /6 SP85 Send Transcription £11.19.0. 
7/- 0329 8/6 AUTOSL1M Standard Auto, £5.19.0. 
10/6 OS01 19/- AT5 Slimline similar to AT*. £7.15.0. 
13/-OABC80 7/- m 0( | cl !,ooo. 10 records, £6.19.0. 
13/-OAF42 ./» Model 2,000- Automatic. £7.19.0. 
10/- OB41 6/0 Mo ,; e | 3,000. Lm-m»« arm. £10.10.0. 
7/BOBC41 7/6| AT ijo. Bias compensator. £11.19.0. 
6/6 0BC81 6/-! A70 . £19.19.0. 
8,'B OBF80 7/9|LAr.80.~ Tranwriiiliou £25. 
11/9 0BF89 7/6' 4f/1 Transcription. £29.19.0. 
8/BOBL21 9/6. Mode i 50- Av.iom.it ic. £9.10.0. 
4/6 PCC189 13/6 OCCS5 7/3 B.S.R. 

11/-PCF80 8/9OCFS0 8/6 ] Gt j; sm^le Deck Complete, £4.5.0. 
S/-PCF82 6/-OCH21 9/3 TJA14 or OA16— Auto Changer, 
3/3 PCF84 12/- OCH42 7/3 » 5 ls n 
3/6PCF86 7/6;DCH81 7/9 

10/: BASE SPEAKERS 

5{S ; 86 WATT. Very heavy coned 12in. 
*{? cast chassis. There is nothing to 
°'° touch it for power hand 
!'.° quality at the price. 

SJglihwft 



6/- PCL82 
7/6 PCL83 
6/9 PCL84 
3/-PCL85 
3/-PCL86 
9/9 PEN25 
9/6 PEN45 
3/9 PEN46 
8/8 PL33 

11/8 PL36 
6/- PL38 

12/6 PLS1 
8/- PL82 
7/B;PL83 
6/6 PL84 
8/6PY31 
7/9PY32 
6/9 PY80 
8/9 PY81 
8/6 PY82 
7/6 PY83 
7/3 PY88 
8/6 PY800 



6K8G 5/- 12SQ7 7/8 EBC33 4/9 EZ40 6/6 PZ30 



7/9 OCL82 
9/-DCL83 
7/3 UF41 
7/6 DF42 
10/0 UF80 
S/9 UF85 
8/6 OF89 
4/B OL41 
8/6 01.44 
9/6 0X46 
17/6 OL84 
7/9 OR1C 
B/6 UHSO 
6/8 006 
7/6 008 
8/- OY21 
10/- OY41 
6/6 OY85 
5/9 VR105 
5/9 VR150 
5/9 X66 
9/-Z66 
8/3 
9/6 



p.p. 



£4.19.0 



Standard Play 




150ft. 2/3 




4/6 




600ft. 7/6 




* >owt. 10/6 




1200ft. 13/8 




Long Play 












900ft. 10/0 




-• 1200ft. 13/- 




* 1800ft. 18/0 





14/- 

Ha 

7/- 
wa 

9/0 

S/9 
11/- 
9/6 
6/- 
5/- 
5/- 
7/9 
MS 

we 



CONNECTING WIRE 

P.V.C. Brleht Colours. Five Ml 
26ft. colls only. */ 

MAINS 
TRANSFORMERS 

Excellent Quality Guaranteed Up- 
right mounting 250-0-250v. 
60mA. rt.Sv.. SA(80mA 12/8) Q ,'fi 
Ditto semi-shrouded. '/• 



CO-AX. low loss, 6d. yd.. 25 yards 
11/8; 30 yds. 22/-: 100 yds. 42/8. 
Co-ax Plugs. 1/3. Wall outlet boxes 3/8 



SPECIAL C.R.T. OFFER 
Due to huge Balk Special Purchase 
we are offering CRM141 and MW 
36/24 Tubes at the unrepeatable 
price of 39/-. P.P. 12/0. The above 
are guaranteed for months. 



• BULK BARGAINS • 

12 POTS, popular values. 6K. to 
J Meg, Unused, mixed pre- Mitt 
set. long sp.. switch, etc. *•/*» 
CONDENSERS. 25 mixed Elect r..> t in 
Many popular sizes. List 4A (- 
value £5. Our p rice > **/ 

100 RESISTORS 6/6 

Excellent. Sizes 4-3 wall. 

100 CONDENSERS 9/6 

Miniature Ceram* anil Silver Mica 
Condensers, 3pF to 6.000pF. LIST 
E OVER £5. 

25 TAG STRIPS 4/- 

1 1. '".. t-way etc. roused. 

100 HI STABS 9/6 

5% 100 n to 3 mn. 



TRANSISTORS 

GOARANTEED TOP QOALITY 
Huge rcdm lion, Red Spot -f C 
standard l.Ftypcnowonly ■ '* 
White Spot Rf 2/- 

12 6 
126 



Mallard Matched Output 
Kits OC81D and 2-OC81 
R.F. Kits OC44. OC45 (2) 

3 trauslstors 



AF114 

AF115 

AF110 

AF117 

AF127 

OC28 

OC36 



8/- 
7/6 
7/6 
7/- 
9/6 
12/6 
14/- 



OC44 

OC45 

OC72 

OC81 

OC81D 

OC82 

OC170 



OC171 8/6 

GERMANIUM DIODES 

General Purpose miniature detector 

8d. 

qr.:i!itv 

1/- 



A.\ 

or 6/6 dox. 

Gold Bonded highest 
Iiiavidually tested. 
9/6 d"/. 

SILICON RECTIFIERS 

Gnataoteod porfonnaoce. Top 

Hake*. Teatco 200v. working 

100mA O /O 250mA T/R 



(3 for 9/8)' 



31O 250m 
9 



19/6) 



ANNOUNCEMENT 

NEW 

BRANCH 



NOW OPE* AT 

10 TOTTENHAM COORT ROAD 

LONDON W.l 



STEREO PORTABLE 
CABINETS 

Latest black and silver metal finish- 
Consisting of centre cabinet size 
Ifljin. x 13in. x 8in. deop with lift up 
'lid together with two 10 x speaker 
'cabinets which clip on ends o( main 
c:i!niiri •■i7.e4jin.xl3in. x 8ln. making 
trvorall size of 25!in. x 141a. x Sin. 
High quality chrome Ottlngs. Will 
toko almost any autochanger or 
tape deck. Approx. S?0 1 Q (1 
half price at *•»»• ■ wrt» 



ARMSTRONG EQOIPMENT. 

Stocked at all branches. 



LOODSPEAKERS 3 Q Top Makes. 

fi = ,D - 7.6 ^4». 8/6 



PRICES SLASHED 

DOLCl (VHF) FM. TONERS MODEL 
FMT5. Self powered 200-250 vac. 
High sensitivity and automatic gain 
Control for long distance reception. 
Size 11}' x SJ" x 31* high. Weight 
7 Jibs. In case finished satin chrntne A 
black. Due to fortunate purchase we 
can oQer limited number of these Hi- 
mstruments | K Qnc 



* TAPE * ; 

H3EAL FOR ANT RECORDER. 
PRICES SLASHED. GUARANTEED 
APPROX. ; PRICE WORLD 
FAMOUS MAIfK BY ENORH008 
PURCHASE. 

Weoflor you fully ten nlll sed polyester' 
mylar and I'.V.C. tapes of quality _ 
hi-li. v.idc range recording character-* 
istics as top grade tapes. Quality 
control manufacture. Try one for 
yourself. They are truly worth a few- 
more coppers than acetate, sub- 
standard, jointed or- cheap imports. 
Try one and prove it for yonrEelll . 

Doable Ptoy -." 

3* 300ft. if-'- 

600ft. 8/- 

5' 000ft. 7/6 5* 1200ft. IB/-, 

5{* 1800ft. 19/6' 

7* 2400ft. 27/- 

Triple Play 
4' 900ft. 13/- 
5* 1800ft. 25/-. 
oi' 2400ft. 34/-' 
7" 3600ft. 44/- 
Quadruple Piny 
3' 600ft. 8/— 
Postage 1/- or Post Free lesa 5% on 
three reels. Quantity and .Iiade 
enquiries invited. 

HITACHI PORTABLE 
TAPE RECORDER 

Fabulous quality and reproduction of 
music. B transistor. I Sin. and 3Jin. 
speeds. Output BOOmW into high 
quality speaker. Ingenious stogie 
control knob. Fast forward and 
rewind. Battery level and record 
t level meter. Fast lead. Precision 
! capstan drive with dynamic earpiece 
monitor recording. Kadip recording 
leads. Outside speaker facilities. The 
most outstanding portable to the 
country 8ize »"/,, x SJ x 65to. 
Genuine uormal price oi 35 gns. 
Unrepeatable. U mon t h s guarantee. 
All spares available. WIU>4 A(£nC 
tape, tape reel, ra Ike. etc. "«»»■ 

HITACHI 4 TRACK MODEL TBA- 
605. This superior AH guinea rccordiug 
machine is on very special limited 
offer. Two channel recording. Playe 
stereo tapes, ljin. and 3iin. speed. 
One track can he listened to on an 
earphone whilst recording on the 
second track, and thereafter both 
tracks plaved simultaneously throcgh 
the loudspeaker. Ideal for languages, 
siogins to music etc. Excellent re- 
production through Hi-Frux. Ellp- 
tical speaker. A.C. erase. Dimensions 
11- x 11- x 6J-". Weight 12 lbs. 
Dynamic mike. Bound love! meter 
Footage indicator. Two AA f^nc 
mixed inputs. *» « n! >- 

HITACHI AM/FM Radios 

Wonderfully styled, guaranteed top 
make. 10-trnnsistor with full long 
and medium waves. Size 95 x 6 s r,, x 
12M/ lc in. Masniilcent reproduction. 
A pleasure to look at. ' An aristocrat 
in its das*." 1 19 mouth- guarantee 
againH faulty mauufacture. Genuine 
retail .price £26.7.6 -t "7 f2tiC 
Unrepeatable. ■ ' Un!>. 



I IK 



C21.13.5 at 



ROBOPHONE ORDERS 
Your C.O.D. order for any items 
exceeding £ 1 can be telephoned to 
BRIGHTON 680722 at any time 
day or night for seven days per 



Post: Ws 



, 2/-. 41 bs. 2/8. 71bs.. 3/6. 15lb»., 4/-, etc. (C.O.D. extra). ALL VALVES LESS 5% AND POST FKEE IN DOZENS. 

Retail only, Hi-Fi demonstration!, 72 East Street, Southampton. Tel. 25S51 
350/352 Fralton Road, Portsmouth. Tel. 22084 
ALL MAIL ORDEli A.ND RETAIL SHOP, 
DEV0NIAM COORT. PARK CRESCENT PLACE. BRIGHTON Tel. 67899 



TECHNICAL TRADING CO. 



1010 



PRACTICAL WIRELESS 



April, 1966 




MAIL ORDERS TO: 
102 Henconner Lane 
Bramley, Leeds 13 

Terms: C.W.O. or C.O.D. No C.O.D. 
under £1. Postage 2/9 extra under £2. 
4/6 extra under £5. Trade Supplied. 
S.A.E. with all enquiries please. 

Personal shoppers welcome at any 
branch below. Open all day Saturday. 

DDAfiCODn 10 North Parade. Tel. 
DKAUrUKU (Halfway We d.) 25349 
nn, r -m, 14 Lower Castle Street 

BRISTOL (Half-day Wednesday) 

T«l.: 22904 

BIRMINGHAM JS&SSS 

Hill Station. CENtral 1279. No half-day 
nCRRY 26 Osmaston Rd.. The Spot 
L»CI\DI ( H a |f-day Wed.) Tel.: 41361 

DARLINGTON ^ H Ky 

Wednescay) Tel: 68043 

EDINBURGH SJ± Kg 

GLASGOW S^affSciT^^SS 

Hill I Sl Savile Street (half-day 
•"W*-»- Thursday) Tel.: 20S05 

I FlfFCTFR 32 Hi « h Street < Half - 

L.CIIC3 I Cl\ day T h U rs.) Tel.: 56420 
I CCftC 5 ' 7 County (Mecca) Arcade 
LLLUJ (No h a|f.day) Tel.: 28252 
I IVFRPftftl 73 Dale St. (No half- 
LIVCnrUUL day) Tel: CENtral 3573 
I rvair.r»il 238 Edgware Road, W2 

LONDON (Half-day Thursday) 

Tel.: PADdington 1629 

MANCHESTER toSST* 

60A-60B Oldham St. Tel.: CENtral 2778 
(Half-day 
Wednesday) 
Tel.: 47096 
\HFFFIFI D l3 Exchange Street 

jncrriLLi/ C a St | e Market Bidgs. 

Tel.: 20716 (Half-day Thursday) 

STAFF REQUIRED. Full or part-time at 
various branches. Experience unnecessary. 

ARMSTRONG, TRUVOX. LEAK, 
QUAD, ROGERS, LINEAR, W.B., 
FANE. WHARFEDALE. GOOD- 
MANS, GARRARD, GOLDRING, 
GRAMPIAN, LUSTRAPHONE, 
SHURE, RESLO, TANDBERG, 
FERROGRAPH Products stocked. 
Usual credit terms available. 



106 Newport Road. 



INTRODUCING A NEW RANGE OF HIGH FIDELITY LOUDSPEAKER UNITS 




AUDIOTRINE PETITE 

Size only 10J x 65 x 7Jin. Rating 3 

watts R.M.S. Frequency range 45- 

20.000 c.p.s. Cabinet beautifully 

finished In Teak (light) or Walnut 

(medium). Fitted specially designed 

Heavy cast 5in. speaker with large 

pole pieces, extra long voice coil and 

plastic treated surround. Impedance 

3 ohms or 15 ohms. Carr. 7/6. 

Or Deposit 27/- and 9 monthly o C n « 

payments ol 17/10 (Total £9.7.6). ■ »«»■ I 

The GLOUCESTER - 

ihne 1 ' cabinet, acoustically _ 

15 ohms. Or Deposit 36/- and q 



The AUDIOTRINE MINI-TEN 

Size only 12}in.High, 61 In. Wide. 8}in 
Deep. Rating 10 watts. Impedance 
15 ohms. De-iuxe Teak or Walnut 
finished cabinet acoustically lined. 
Heavy cast oin. Bass spoakor with 
extra high flux density ceramic 
magnet plastic treated surround and 
long voice coil giving low fundamen- 
tal resonance. Choke/Capaci ty Cross- 
over and Tweeter. Really astound- 
ing performance. Frequency range 45-20.000 



i c.p.s. Or Deposit £2 and 12-i-GnS. 

9 monthly payments 27/9 ■ * 2 w, f ' 

Handsome ••slimline" cabinet, acoustically I <To*aJ £H.:i.o>. _Ca n\ 8/o 

lined. Size 24in. High. 20in. Wide, 6iin. Deep. I 7TZ RR0NTE 



monthly payments of 4 \ fine 
24/8 (Total £13.18.0). ■ ■ »••»• 
Carr. 15/- 
The DORCHESTER 

Attractive cabinet in luxurious 
Teak or Walnut finish. Acousti 
cally lined. Size 24in. High. 15in. 
Wide. 8}in. Deep. Incorporating 
specially designed lOin. Heavy cast 
speaker with massive 2in. polo 
pieces and dual cone with plastic 
treated surround. Frequency res- 
ponse 20-20.000 c.p.s. Rating 15 watts Hope- 




Deep. Fitted Wlianedale Super 8 
R3DD Speaker, with Roll sur- 
round and dual cone. Rating 6 
watts. Impedance 15 ohms. 
Or Deposit 39/- and -|2 GllS. 

Carr. 15/- 



i monthly payments 
26/10 (Total £14.0.6). 



The STANWAY 

Attractive contemporary styled 
cabinet finished Teak (light) or 
Walnut (medium). Acoustically 
lined. Size 24in. High. 20in. Wide. 
8Jin. Deep. Fitted 12in. high flux 
Bass speaker with plastic treated 
surround giving extremely low fundamental 



dance 15 ohms. Or Deposit 48/- 1 C fine surround giving extremely low lundamenwu 
and 8 monthly payments 33/- ' ° » l,s » resonance and high sensitivity. '1 he smooth 



(Total £17.7.3). 



Carr. 16/- 



W.B. "STENTORIAN" HIGH FIDELITY 
P.M. SPEAKERS I1FI012. 10 watts rating. 
Where a really good quality speaker at alow 
price is required we highly recommend this 
unit with an amazing perform- 
ance. Please state whether 3 CA 1Q Q 



frequency response 20-20.000 c.p.s. is 
achieved by addition of high flux tweeter 
and cross-over unit. Rating 20 watts. 
Impedance 15 ohms. 

Or Deposit 3 Gns. and 12 IQlfinS 
monthly payments 32/6 ,i7 2 w '*' 
(Total eti.ta.O;. Carr. 



or 15 ohms required. 



SCOOP PURCHASE OF HIGH QUALITY 

RECORD CHANGERS 

Brand new Garrard 3000 LM. I fl 

Very latest model. Normal |y 

Retail price approx. £12.15.0. 

Heavy Turntable. Sonotone Low Mass 

Stereo/Mono cartridge. Fully guaranteed. 



Cut. 5/6 

Gns. 



AUDIOTRINE HFI00D lOin. 
15 Watt HI-FI Loudspeakers 

Heavy cast construction. / 
Dual cone. Plastic treated 
surround. Smooth irequency 
response 20-20.000 c.p.s. Out- 
standing performance »c « 
Speech coll 3 or 15 ohm. *»•! 
Exceptional value at Carr. : 




AUDIOTRINE HI-FI LOUDSPEAKER ENCLOSURES 



All Upon of pleasing modern 
•'slimline" design acoust- 
ically lineal ami in alterna- 
tive finishes of light teak 
or medium walnut. 
SE8 Designed for optimum perfor- 
mama wlttianv lli-l-'i sin. speaker 
Si.-r gejo, high: 151n. wide: 7ln. 
deep. Or deposit CMCA 
18/- and 9 monthly *>«• ' **mV 
paviDruls of 12/3 Cnrr. T'll 
(Total 86.8.3). 




SE10 For lOin. High Fidelity Speaker with provision 
(or tweeter. Especially recommended for use with 
Andiotrine HF100D speaker. Slue 8410. high: 161 
wide: Tin. deep. Or deposit 21/- CR 1QQ 

and 8 monthly payments IS/- *"'• ■ 9m9 

iTotal £7.16.0). Carr. 10/ 

SE12 For outstanding performance with any 12In. 
BJ-Fi speaker but especlully suitable (or types with 
low fundamental resonance. A tweeter cut-out is 
provided. Size 94 X 20 x 71n. approx. Or depoult 
27/- and H mojithly payments. _ O fine 



17/10 (Total £8.7.6). 



i.i 



in 



R.S.C. SUPCR lSWFtAA9PUFte*\R.SC $UP€&$OST€*eQAMPUfm 




put za watts. • x.v.v:'",', ,, ..* . ;»,. 'i ■-., \,,- - ; v.i'-f i 

PRINTED CIRCUIT CONSTRUCTION.! HER.-. A I .'-.I I I MLS 1IIL IOST. I 
LATEST MULLARD TRANSISTORS '— ■ — — "- — — — — — — — — — > 

■ 




x*p3°nm/vt* 



AD149. AD141. OC127Z. OC81Z. OC44. 
OC44. OC81Z. OC44. AC107. 
5 POSITION INPUT SELECTOR 
SWITCH EQUALISATION to 

Standard R.I.A.A. and C.C.I.R. Char- 
acteristics for Oram and Tape Heads. 
11 I.L TAPE MONITORING FAC- 
ILITIES. 

SENSITIVITIES: Magnetic P.U. 4 
mV. Crystal or Ceramic P.U. 400 mV. 
Microphone 4.5 mV. Tape Head 
2.5 mV, Radio/Aux or Ceramic P.U. 110 mV. 
FREQUENCY RESPONSE: 20-20.000 c.p.s. 
TREBLE CONTROL: + 15dB to — 14dB at 
10 KO/8, 

B \.ss CONTROL: + 12dB to — 15dB at 50 c/s. 
HARMONIC DISTORTION at 10 Watts 
R.M.S. 1.000 c.p.s. 0.35",,. HUM LEVEL: — 75dB. 
NEGATIVE li:i:DBA«'K:52dB. - rt 

Complete Kit of parts with full constructional "I fl 
details and point to point wiring diagrams. |U, 
Or St with Printed Circuit wired and tested 30/- w * GNS. 
extra or Deposit 72/- and 9 mthly pymts 22/6. (Total £13.14.6) 
Attractive Walnut or Teak finished cabinet 5 Gns. ia i 
orDeposltl7/-and9monthlypaymentsll/-. Total "»5 Carr. 
£5.16.0.0runitlaotorybuiltandtested. complete GNS. 12/6 . 
with cabinet and with our usual 12months' guarantee. 
Or Deposl t £3.9.0 and 9 monthly payments £2. Total £21.9.0. 
ALL COMPONENTS ETC. ARE OF A HIGH STANDARD 
AND SUPPLIED BY LEAJDLNG BRITISH MAM 1 At - 
TURERS. Send S.A .E. for leaflet. 



©U® & & ® 



U4MUS 




1 Carr. 

2 - 10/ - 



A DUAL CHANNEL VERSION OF THE 
SUPER 15. Employing Twin Printed Cir- 
cuits. Close tolerance Ganged Pots. Matched 
Components. 

CROSS-TALK: — 52dB at 1.000 C.p.s. 
CON 1TIOLS: 5 position Input Selector. Bass 
Control, Treble Control. Volume Control. 
Balance Control. Stereo/Mono Switch Tape 
Monitor Switch. Mains Switch. 
INPUT sockets fMatohed Pairs) 
<ii Magnetic P.U. (2> Ceramic or 
Crystal P.U. (3) Radio/Aux. I) Tape 
Head/Microohone. 

Operation of the Input Self for Switch 
assures appropriate equalisation. 
Rigid 18 s.w.g. Chassis. Size approx. 
12" Wide. 3" High and 8 - Deep. 
Attractive Fascia Plate and Matching 
Knobs. Neon Panel Indicator. 
Above facilities, etc.. except for Gang- 
ing and Balance Control, apply also to 
Super 15. 

THESE UNITS ARE EMINENTLY 
SUITABLE FOR USE WITH ANY 
MAKE OF PICK-UP OR MICRO- 
PHONE (Crystal, Ceramic. Mncnetlf. Moving Coil, Ribbon) 
< I RRENTLY AVAILABLE REGARDLESS OF THE 
COST. SUPERB SOUND OUTPUT QUALITY CAN BE 
OBTAINED BY USING WITH FIRST RATE ANCILLARY 
EQUIPMENT. All required parts, point to point ■ a Carr. 
wiring diagrams and detailod instructions. I 3* 12/6 
II required printed circuits can bo supplied with ■ V GNS. 
appropriate components assembled, soldered and tested for 
£8.0.0 extra. Terms: Deposit 6 kiik. & 9 mthly payments 38/6. 
Total £23.12.6. Attractive Walnut or Teak finished Cabinet 
5 gns. or Deposltl"/- & 9 monthly payments 11/-. Total £5.1 6.0. 
Or unit completely assembled ready for use housed 
In Cabinet. Or Deposit £4.12.0 and 12 monthly pay- 
ments 48/-. Total £33.8.0. Carr. 15/- 



IMHOHTANT VOTE. Rated output 
figures arc given In R.M.S. and not speech 
and music or I.H.F.M.. otherwise we could 
obviously quote much higher outputs. 



29 GNS. 



April, 1966 



PRACTICAL WIRELESS 



1011 



R.S.C. STEREO 20 HIGH FIDELITY AMPLIFIER 

PROVIDING 10/14 WATT ULTRA LINEAR 
PUSH-PULL OUTPUT ON EACH CHANNEL 

SUITABLE for "MIK K", GRAM, RADIO or TAPE. 
Employing valves BOC83, B0088, ECL8G, ECL8U, 
ECL96, ECL80, EZ81. Send S.A.E. lor leaflet. 
FREQUENCY" KKSrONSE ±2dB. 30-20.000 o.p.B. 
HUM LEVEL UOdB down. 
SENSITIVITY: 5 millivolts maximum. 
HARMONIC DISTORTION (each channel) 0.2%. 
Output transformers are hlith.quallt-y Bccfionally 
wound to required specification. Output matching 
for 3 and 15 ohm speaker-* 00 each ^m m Carr. 12/11 
channel. Complete set of parts with 1 ij fine 
point-to-point wirluu diagrams * ** WHO. 
and instructions, or Factory assembled, le.-t od and 
supplied with our usual 12 months" guarantee for 
1 O Carr. 12/6 Or DEPOSIT 57/- 




R.S.G.A1520WATTR.M.S. 

HIGH FIDELITY TRANSISTOR AMPLIFIER 
With integral pre-amp tone 
control stages 

Output for 3, 7.3 and 15 ohm speakers. 



■* Four-position tone compensation 
and Input Selector switch. 

* Will amplify direct Irom 
Heads. 

it Stereo/Mono switch, 

* Separate Bass "Lift" and 
and treble "Lift" and "Cut' 
trols. 

■jc Neon Panel Indicator. 

-k Handsome Perspei Frontplate. 




Tape 



"Cut" 
oon- 



GNS. 



payment* 39/10 (Total £20.15.6). 



Kit of parts consisting of Printed Circuit 
and all components for same Including 9 
Milliard or Newmarket latest type semi- 
conductors. Heat sink and : till wiring 
Instructions or with printed circuit fullv 
wired ami tested £2 extra. 
Frequency Response -ldii 

000 c.p.s. 
Harmonic Distortion 0.1% measured at 1000 c.p.s. 
Hum and Noise — SOdB. Sensitivity SJniT. 
Bass Control +9dB to — HdB at 40 cp-s. Treble Control 
+ 8dH to — l.ldB at 10 Ko/s. 
Suitable Power Pack Kit 39/6, Or ready built 59/6 



£6.19.9 



Post 5/- 



AUDIOTRINE HI-FI TAPE RECORDER KIT 

REALISM AT INCREDIBLY LOW COST. CAM BE 

AS-StMBLED IN AN IIOUR. 

ONLY 4 PAIRS OF SOLDKRED JOINTS PLC'S MAINS. 

Incorporating the latest Magnavox Tapedeck. The Audio 
trine High Quality Tape Amplifier with switchec 
equalisation for each of 3 speeds. High Flux P.M. Sp 
empty Tape Spool, a Reel of Best Quality Tape ar.u ^ 1i.it i 
some Portable Carrying Cabinet of latest styling ana !ini.~he( 
dark grey leathercloth with silver/chrome fittings, etc. SiM 
14} x 17 x 8Jin. high and circuit. Total cost if purchascJ ind,- 
vidually approx. £35. Performance equal to units in the £50- 
£60 class. S.A.E. for leaflets. TERMS 

AE1 Carr. 18/6 Deposit 4ens. and 12 monthly paymoi 

4h V2 QnS of _42/-. (Total 28 Un*.). 



4Trac 



:-.:-- 



el 3 tin*, extra. 




R.S.C. AI0 30 WATT ULTRA LINEAR HIGH FIDELITY AMPLIFIER 

A highly sensitive Push-Pull high output unit with self-contained Pre- 
amp./Tono Control Stages. Performance figures compare equally 
with most expensive amplifiers available. Hum level — 70dB. 
Frequency response = 3dB 30-20.000 c/s. A specially designed sec- 
tlonally wound ultra linear output transformer is used with 
807 output valves. All first grade components. Valves EF86. 
EF86. ECC83. 807. 807. GZ3-1. Separate Bass and Treble Controls. 
Minimum input required for full output 12 millivolts so that 
any kind of Microphone or Pick-up is suitable. Tlio unit 
is designed for Clubs. Schools, Theatres, Dance Halls or 
Outdoor Functions, etc. For use with Electronic Organ, 
Guitar, String Bass, etc. Gram. Radio or Tape. Output Soekot provide* L.T. and H.T. 
for Radio Tuner. Two inputs with associated volume controls so that two separate inputs 
such as Gram and "Mike" can be mixed. 200-2S0V. 50 c/s. A.C. Mains. Output for 3 and 15 
ohm speakers. Complete kit of parts with fully punched chassis and point-to-point wiring 
diagrams and instructions, in f2nc Carr. Supplied factory built with EL34 output 
t£. una. jo/, valves and 12 months' guarantee for 15 
Gns. If required perforated cover with carrying handles can be suppl'.ed for 21/-. Send 
S.A.E. for leaflet. TERMS: Deposit 48/- and 9 monthly payments oi 33/3 Total £|7.7.3> 




HIGH FIDELITY 12-14 WATT AMPLIFIER TYPE A11 

PUSH-PULL ULTRA LINEAR OUTPUT "BUILT-IN- 
TONE CONTROL PRE-AMP 

Two input sockets with associated controls allow mixing of 
"mike" and gram. etc.. etc. High sensitivity. Valves ECC83. 
ECC83. EL84. EL84. EZ81. High Quality sectionaUy wound out- 
put transformer specially designed lor Ultra Linear operation 
and reliable small condensers, etc. INDIVIDUAL CONTROLS 
FOR BASS AND TREBLE "Lift" and "Cut". Frequency res- 
ponse r 3dB 30-20.000 c/s. Six negative feedback loops. Hum 
level— 60dB. SENSITIVITY 23 millivolts. Suitable for Crystal 
or Ceramic P.U.'s all types "mikes". Comparable with the 
very best designs. For Musical Instruments such as String Bass, Electronic Guitars, 
etc. Output Socket provides 300v. 30mA. and 6.3v. 1.5a lor supply oi a Radio Tuner. 
Size approx. 12x9x7in. For A.C. mains 200-250v. 50 c.p.s. Output lor 3 and 15 ohm speakers. 
Kit complete to last nut. Chassis fully punched. Full instructions and point-to-point 
wiring diagrams supplied. Only O f2nc Carr. 

(Or factory built 51/6 extra). *» «'•*• 10/- 

Metal covers with 2 carrying handles can be supplied lor £1. TERMS ON" ASSEMBLED 
I NITS: Deposit 33/3 and 9 monthly payments ol 24/1 (Total £13.10.0). Send S.A.E. for 
tiii-.-iiy.icu leallet deuuiii.g Cabinet..-. Speakers. M.kc-. etc 



R.S.C. STEREO/TEN HIGH QUALITY AMPLIFIER 




A complete set of parts for the construction of a stereo 
amplifier giving 5 watts hlghquallty output on each chan- 
nel (total 10 watts). Sensitivity is 50 millivolts. Suitable 
all crystal or ceramic stereo heads. Ganged Bass and 
Treble Control give equal variation of "lift" and "cut". 
Provision Is made for use as straight (monaural) 10 watt 
amplifier. Valve line-up ECC83. ECC83. EL84, EI.84, EZ81. 
Outputs for 2-3 ohm speakers. Point-to-point wiring 
diagrams and instructions supplied. Send S.A.E. ror 
leaflet. g GnS. 



Or supplied factory assembled with 12 months' guarantee for £11.7.6. 
Terms: Deposit 2 Gus, and 9 monthly paymc n ts Q! 24/2 'Total £rj.li).ti",. 



Carr. 10/- 



R.S.C. 4/5 WATT A5 HIGH GAIN AMPLIFIER 

A highly-sensitive 4-valve duality amplifier for line home 
small club, etc. Suitable for all crystal or ceramic F.IL 
heads and practically all "mikes". Separate Bass and 
Treble controls giving "lift" and "cul". Hum level TldB 
down. Negative Feedback 15dB. H.T. or SOOv. HmA and 
L.T. of 6.3v. 1.5a, available for supply of Radio Tuner or 
Tape Deck Pre-amp. For A.C. mulns 30<)-350v. Speaker 
output 3 ohms. Kit Is complete In every detail with fully 
punched Hammer finished chassis, point-to-point wiring 
diagrams and Instructions. Exceptional \nlue CA 1 E A 
or assembled ready for use 25/- extra, plus 3/6 carr.. deposit 22/8 and ■*"■» ■ »*■»» 
5 monthly payments of 22/6 (Total £6.15.0). for assembled unit. 




INTEREST CHARGES REFUNDED 

ON H.P. ACCOUNTS SETTLED IN 6 MONTHS 

LINEAR TAPE PRE-AMPLIFIER. Type LP' I. 

Equal.satlou. Positions for Be 
Hi I; in.. :i;m.. r; in. per sea., and Playback, i m- i 
Recording Level Indicator. Designed primarily 
an the link betareen ri Magnavox Tai-e Peck and 
Hi-Fi amplifier suitable almost any ft I fjrlg 
Tape Deck. B.A.B. for leaflet. ° 2 « ,,a « 



CORNER CONSOLE CABINETS 

Strongly made. Beautiful 
I ,, .: i - >i --. i walnut veneered 
linish. Pleasing design. 
JUNIOR MODEL. I'.. i 
up to Sin. -peaker. 
Approx. 20 x II An .ft 
I bin. Carr. Bit. *»«/» 
STANDARD MODEL. To 
take up to lOin. speaker. 
Size 'J7 x 18 x Win. 

5 GnS. carr. 7/6. 

SENIOR MODEL. To 

take up to 12ln. speaker 

and with Tweeter cut-out. Size approx. SO x SO 

x 15in. (Recommended for use with Audiotrine 

speaker r-vstein.l Carr. 8/6. 

Terms available. 




8 Gns. 




l2in.HIGH QUALITY LOUDSPEAKERS 

In walnut veneered cabinet. 
10 WATT MODEL. Gauss 
12.000 lines. Speech coil 3 or 

ia ohms. £4 10-6 

Carr. 5 6. **•■ ■ «'■«' 

Terms: Deposit 15/- and 9 

monthly payments of 10/10 

(Total E6.12.6j. 

20 WATT MODEL. 15 ohms. 

-Size \t x 18 x lOin. 

Terms: Deposit 24/6 and 9 

m mtr.ly pa.vm.ints oi 17/- 

(Total £8.17.6). Carr. 8/8. 

30 WATT MODEL. IS obm* 

Carr, 10 ■ at Deposit 35/- and 9 

m atari payments of 22/- (Total £11.13.0). 

Any ot above in extra heavy rexine covered 

Cabinets, £1 extra. 




£7.19.6 
10 Gns. 



R.S.C. JUNIOR BASS REFLEX CABINET. Deslan- 
ed for any good quality Bin. or loin, speaker. 
Acoustlcnilr lined and ported. Polished Walnut 
vcneui finish. Ki/.c- IS x 12 x lorn. SUongtJ 
made. Handsorut.' appearance. Superb CA 7 ft 
reproduction. Carriage 3/-. *r». f .W 



Al DIOTRLNE HI-FI SPEAKER 
SYSTEMS Consisting or matched 12in. 
12.000 line. 15 ohm high quality speaker: 
cross-over unit (consisting 
of choke, condenser, etc.). 
and Tweeter. Smooth res- 
ponse and extended frequen- 
cy range ensure surprisingly 
realistic reproduction. 

Standard 10 watt rating. 

&!«• £4.19.9 

Or Senior 20 watt. £6.19.6. Carr. 7/6. Or 
Deposit 21/- and 9 monthly payments of 
15/- (Total £7.Hi.0). 




TWEETERS Fane 3 ohm or 15 ohm 25/9. 



R.S.C. BABY ALARM or INTERCOMS! 

KIT.. AH parts with diagrams etc. In two 
polished walnut finished cabinets of 
pleasing design. High sensitivity. For 
200-2SOV. A.C. mains. Fully isolated. 
Controllable at both units. A unit of this 
class would normally cost £20-£30. Only 
89/6. carr. 5/-. Ready for use, 6 Gns. 



1012 



PRACTICAL WIRELESS 



April, 1966 



R.S.C. BASS-REGENT 50 WATT AMPLIFIER 

AN EXCEPTIONALLY POWERFUL HIGH QUALITY ALL-PURPOSE UNIT 
For lead, rhythm, bass guitar and all other musical instruments 
For vocalists, gram, radio, tape and general public address 

•k UNUSUALLY POWERFUL LOUDSPEAKER COMBINATION 
consisting of a FANE HIGH FLUX 15in. 30 watt unit PLUS 
a FANE 12in. 20 watt unit with extended frequency response. 
4 Jack Inputs and two Volume Controls for simultaneous use 
of up to 4 pick-ups or "mikes". 

• Cabinots covered in two-tone Rexlne/Vynair with gold 
trimming. 

* Separate Bass and Treble Controls giving 'lift' and 'cut'. 
Send S.A.E. for leaflet. Or call at one of our branches and com- 
m f\ pare with units at three times the cost. 

4H OSS. Or deposit of£7.l6.0 and 12 monthly payments of 
^ w Carr. 25/- 81/6 (Total 54 mis.). 




INTEREST CHARGES 
REFUNDED on n y. 
ACCOUNTS SETTLED IN 



RSG 



6 MONTHS 



Addresses Page 1010 



R.S.C. B20 MULTI-PURPOSE AMP. 
especially suitable for Bass Guitar 

With Massive 15in. high flux loud- 
speaker. Rating 25 watts. Indi- 
vidual bass and treble controls. 
Two jack inputs separately con- 
trolled. Heavy cabinet attrac- 
tively finished in Rexlne/Vynair. 
Size approx. 24 x 21 x Ilia. 
Send S.A.E. for <>Q± fJnc 
leaflet. Carr. 17/6 *»T Wlia. 
Or deposit £4.14.6 and 12 monthly 
payments of 49/- (Total 3S t gns.i. 



R.S.C.GI5 IS WATT AMPLIFIER for Lead 
or Rhythm Guitar, Mike, Gram or Radio 



High-fldellty output. Separate bass 
and treble controls. Twin separate, y 
controlled Inputs. Heavy Duty 12in. 
20 watt Speaker. Cabinet covered 
n attractive Rexlne/Vynair. Size 
approx. 18in. x 18ln. iini ** • 
8in. S.A.E. for leaflet. I y-k llllS. 
Carr. 12/6. ' ' 2 w "*' 

Or Deposit 3 En*, and 12 month.y 
payments of 32/6 (Total £25.13.0). 




R.S.C. COLUMN SPEAKERS 

Covered in two-tone Rexine/ 
V.vnalr. Ideal for vocalists and 
Public Address. Normally sup- 
plied for 15 ohm matching but 
can be supplied for lOOv. line 
for 35/- extra. 

Type C58, 15-20 watts. Fitted 
five 8in. high flux speakers. 
Overall size approx.42xl0x5in. 
1 O I Rne Carr. Or deposit 
IZ-£ una. 10/ . £2 and 

B monthly payments of 27/9 
i Total £14.9.9). 
Type C-112. 40 watts. Fitted 
four 12in. 12.000 line 10 watt 
sDeakers. Overall size 56 x 14 x 
9in. approx. -IQi fine 
Carr. 15/- '*»2 unb ' 

Or deposit 3 pus. and 9 mthly. 
pymts. 43/2 (Total 21i wis). 



liii 



JASON FMT1. VHF/FM Radic 
design. All parts inc. valves. C( 
tuning dial, escutcheon, etc. ** 



TRANSISTORISED SOUND MIXER 

Enables mixing of up to 4 standard lack inputs, 

T ANNOY RR-ENTKAST LOUD- I '- e ' mlc " tape. gram, tuner, etc.. into single 

SPEAKERS. For outdoor'or 97 leCarr \ output. Compact and completely self- AQ /Q 

*' /° 4/a I contained, uses standard 9v. battery. ^**» ** 



factory use. 8 ohms, 8 watts. 



R.S.C. MAINS TRANSFORMERS (fully guaranteed) 



Interleaved and Impregnated. Prim- 
aries Mmial v. J0 en. Screened. 
MIDGET Clamped Type 21 x 21 x 2JIn. 

250v. 60 mA, 6.3v. 2a 13/9 

250-0-250V. 60mA. 6.3v. 2a . . . . 14/9 

TOP SHROUDED DROP THROUGH 
250-0-250V. 70mA, 6.3v. 2a, 0»5-6.3v. 2a 17/9 
350-0-350V. 80mA, 6.3v. 2a. 0-5-6.3v. 2a 21/9 
250-O-250V. 100mA. 6.3v. 2a. 6.3v. lu . . 21/9 
250-0-250V. 100mA. 6.3v. 3.5a. C.T. . . 19/9 
250-O-250V. 100mA. 6.3v. 4a. 0-5-6.3v. 3a 28/9 
300-0-300V. 130mA. 6.3v. 4a, 6.3v. la, for 

Mullard 510 Amplifier 35/9 

300-O-300V. 100mA. 6.3v 4a. 0-5-6.3v. 3a 28/9 
350-0-350V. 100mA. 6.3v. 4a. 0-5-6.3V. 3a 28/9 
350-0-350V. 150mA. 6.3v. 4a. 0-5-6.3v. 3a 37/9 
FULLY SHROUDED I riiKilll 

25OO-250V. 60mA. 6.3v. 2a. 0-5-6.3V. 2a 

Midget type 2J x 3 x 3in 18/9 

250-O-250V. 100mA. 6.3v. 4a, 0-5-6.3V. 3a 29/9 
300-0-300V. 100mA, 6.3v, 4a. 0-5-6.3v. 3a 29/9 
300-0-300V. 130mA, 6.3v. 4a. C.T. 6.3v. 

la. for Mullard Amplifier . . . . 36/9 
350-0-350V. 100mA. 6.3v. 4a. 0-5-6.3v. 3a 29/9 
35O-O-350V. 150mA. 6.3v. 4a. 0-5-6.3v. 3a 38/9 
425-0-425V. 200mA. 6.3v. 4a. C.T. 5v. 3a 57/9 
425-0-425V. 200mA (6.3v. 4a Twice), 5v. 3a 59/9 
450-0-450v. 250mA, 6.3v. 4a. C.T. 5v. 3a 69/9 



FILAMENT TRANSFORMERS 

200-250V. 50 c/s primaries 6.3v. 1.5a, 6/6: 6.3v. 
2a. 7/6: I2v. la. 7/11: 6.3v. 3a. 8/11: 6.3v. 6a. 
17/6: I2v. l.5a twice. 17/6. 

OUTPUT TRANSFORMERS 

Standard Pentode 5.000 Q to 3 a .. 6/6 

Standard Pentode 7.000 Q to 3 Q .. 6/6 
Push-Pull 8 watts. EL84. or 6V6 to 3 f! 

or matched to 15 tl 9/9 

Push-Pull 10-12 watts to match BV6 or 

EL84 to 3-5-8 to 15 Q 19/9 

Following types for 3 and 15 a speakers : 

Push-Pull 10-12 watts. 6V6 or BL84 . . 18/9 

Push-Pull 15-18 watts. 6L8, KT66 . . 22/9 
Push-Pull Mullard 610 Ultra Linear . . 29/9 
Push-Pull 20 watts, sectlonally wound 

6L. KT66. EL34. etc 49/9 

SMOOTHING CHOKES 

60mA. 10H 400 Q 4/11. 100 mA. 10H. 220 8/9 

80mA. I0H 350 H 5/9. 150mA. 10H. 250 Si 11/9 

CHARGER TRANSFORMERS 

AU with 200-240-250 v. 50 c/s Primaries: 

0-9-15V. lia. 12/9: 0-9-15v. 2a, 14/9: 0-9-15v. 

3a. 16/9: 0-9-15v. 5a, 19/9: 0-9-l5v. 6a. 23/9: 

0-9-15v. 8a, 28/9. 

AUTO (Step up/Stop down) TRANS. 

0-110/120-230/250V. 60-80 watts, 13/9: 150 

watts. 27/9: 250 watts. 49/9: 500 watts. 99/9. 



30 WATT HI-FI AMPLIFIER 
For ELECTRONIC ORGAN. GUIT- 
AR, VOCAL or INSTRUMENTAL 
GROUPS 

A Four Input, two vol- 
ume control Hi-Fi unit 
with separate Bass and 
Treble •cut' and 'boost' 
controls. Latest type 
valves. Sti-ong Rexine 
covered cabinet. At- 
tractive Black/Gold 
fascia plate. For 200- 
250v. A.C. mains. Output for 3 or 15 ohm 
speakers. Send S.A.E. Tor leaflet. 
Carr. 12/6 or Deposit £3 and 9 mthly. 

17 fine payments of 37/- (Total 
I I Ulia. C1Q13.0). 




I8.n. 60 WATT EXTRA HEAVY DUTY 

LOUDSPEAKERS Famous Carr. 15/- 
make. Normal price over *f fine 
£26. Very limited number • • **"»• 
to clear fully guaranteed. Terms available, 

LINEAR TREMOLO PRE-AMP UNIT 

I Suitable for use with any of our Amplifiers 
i Controls are Speed (frequency A fine 
I of interruptions;. Depth (for ^ who. 
I heavy or light effect). Volume and Switch. 

SELENIUM RECTIFIERS fw . (B ridged) 
6/l2v. la. 3/11: 6/l2v. 3a. 9/9: 6/l2v. 6a. 15/3: 
6/12v. 2a. 6/11: 6/12v. 4a. 12/3: 6/12v. 10a.26/» 



R.S.C. BATTERY CHARGING EQUIPME 

All for A.C. Mains 200-250 v. 50 c/s 
Heavy Duty 




Assembled 
lamps (/Uv. 

Fitted Am- 
meter and 
variable 
charge rate 
selector. 
Also selector 
plug for 6 v. 
or l2v. charging. Louvred steel case 
with stoved grey hammer llnish. Fused 
and ready for use with mains rn/fl 
and output leads and clips. JlH'H 
Or Deposit 12/- and 5 monthly**" ** 
payments of 12/- Total £3.18.0. Can. ■! ■; 



Charger Kit 
6/12v. 6 amps., 
variable output. 
Consists of Main 
Transformer 0- 
200-230-250V. : FW 

(Bridge) Selen- 
ium Rectifier: 
Ammeter. Vari- 
able Charge Rate 
Selector Panels. 
Plugs. Fuses. 
Fuseholder and 

1 59/9 



Carr.5/6. 



NT Guaranteed 12 months 

BATTERY CHARGER KITS 

Consisting of Mains Trans- 
former. F.W. Bridge. Metal 
Rectifier, well ventilatedsteol 
case. Fuses. Fuse-holders. 
Grommets. panels. Heavy 
Duty Clips, circuit. Carr. 3/6 
6v. or 12v. 1 amp. . . 22/9 
As above wl th ammeter 28/9 
6v. or 12v. 2 amps . . 25/9 
6v. or 12v. 2 amps, Inclu- 
sive of ammeter . . 36/9 

6v. or 12v. 4 amps with 
Ammeter and variable 
ehurge rate selector . , 52/9 
CHARGER AMMETERS 

0-1. 5a. , 0-4a.. 0-7a.. 8/9 each. 



COMPLETE POWER PACK KIT 

Consisting of Mains Trans. Metal Recti- 
fier. Electrolyucs. smoothing choke, 
chassis and circuit. 200-250v. 1Q/-|1 
A.C. mains. Output 250v. 60 , */ M 
mA. 6.3v. 2a. Or with case in lieu of chas- 
sis 25/-. 



R.S.C. BATTERY TO MAIN'S CON- 
VERSION UNITS. Type 
BMI. Battery elimi- 
nator. Size 5! x 4J x 
2ln. approx. Com- 
pletely replaces bat- 
teries supplying 1.4v. 
and 90v. where A.C. 
mains 200-250v. 50 c/s 

is available. Complete kit with diagram 

39/9 or ready for use 49/9. 




EX GOVT. SELENIUM 
RECTIFIERS I2v. 15 AMP 
(BRIDGE) F.W. ONLY 



19/9 



R.S.C. GRAM AMPLIFIER KIT. 3 watts, 
output. Negative feedback. Controls: Vol.. 
Tone and Switch. Mains operation 200-250v. 
A.C. Fully isolated chassis. Circuit, etc., 
supplied. Only 39/9- Carr. 3/9. 



R.S.C. 4 WATT GRAM. AMPLIFIER 
KIT. Complete set of parts to build a good 
quality compact unit suitable for use with 
any record playing unit. Mains Isolated 
chassis, separate Bass and Treble rf\tr\ 
controls. Output for 2-3 ohm 3*//*/ 
— ' — For 200-250V. A.C. ** * 



HI-FI 12 WATT AMPLIFIERS 

BRAND NEW Carr. 7/6 C7 1Q Q 

EX-GUITAR AMPLIFIERS *f.l».» 

Manufacturers' discontinued Model. 
Push-pull output. Latest high efficiency 
valves. Dual separately controlled Inputs 
for 'Mike' and gram. Separate Bass and 
Treble Controls. High Sensitivity. Out- 
pui for 3 or 15 ohms speaker. Guaranteed 
tested and In perfect working order. 



TRANSISTOR SALE Mullard OC7i 2/11. 

OC45 3/11. OC44 3/11. OC72 2/11. 0081 2/11. 
OC171 8/9. AF117 6/9. Edlswan XA101 3/9. 
XA112 3/9. XCI01A 3/9. Postage 6d. Tor up 
to 3 transistors. 




COMMUNICATION RECEIVERS 
RX 60 DE LUXE 
4 HAND 

220/240V. 50/ ••:' .-.-■ ■ ■■■■■■ 

60 o.p.s. A.c.r 
mains oper- 
ation. Pre-: 
quencies cov- 
ered. 638 Ke/s 

to 30 Bora 

continuous 
Integral PM. 
Speaker. Slide rule tuning dial 'S' meter. 
Phone Jack. Powerful built-in antenna 
for long range reception. Stand-by Switch 
with terminal for transmitter. Other feat- 
ures are bandspread tuning. Noise limiter 
A.V.C.. B.F.O, Size approx. 13! x 53 x 8iln. 
Handsome metal cabinet with chrome fit- 
tings. Brand new with full instructions. 
Usual guarantee. Or deposit 1Q (2nc 
£5 and 9 monthly pymts. * 9 who. 
37/8 (Total £21.19.0). Carr. 10/- 



April, 1966 



PRACTICAL WIRELESS 



1013 



BENTLEY ACOUSTIC CORPORATION LTD. 

Suppliers to H.M. Government. 38 CHALCOT ROAD, LONDON, N.W.I Telephone: primrose 9090 

NEAREST UNDERGROUND: CHALK FARM. ALL GOODS LISTED BELOW ACTUALLY IN STOCK. ALL 

GOODS ARE NEW, BEST QUALITY BRANDS ONLY. AND SUBJECT TO MAKERS' FULL GUARANTEE, PLEASE 
NOTE THAT WE DO NOT SELL ITEMS FROM USED EQU IPMENT NOR MANUFACTURERS' SECONDS & REJECTS. 
WHICH ARE OFTEN DESCRIBED AS NEW AND TESTED" BUT HAVE A SHORT AND UNRELIABLE LIFE. 



- 
4/6 LZ319 6/6 
7/6 I.Z329 6/6 
7/3 MHD4 7/6 
2/6 MUI.D412/6 
5/ - ML8 5/9 

MS4B 20/5 
M8P4 12/- 
MU 12/ 14 4/6 
M X in 8/9 
N37 10/8 



lO) 

1C2 
1C3 
1C3 
106 

IDS 
1D6 

1FD1 
1FD9 
1G6 



6C6 

6C8 
6C9 
6C10 
6UI2 



OA2 5/8 | 6BX6 
OB2 6/- 6C4 

OZ4GT 4/3 6C5 
1A3 2/6 

1A4 12/8 
1A5 5/- 

1A7QT 7/6 

4/- 

8/- 

6/6 

5/- 
10/0 
0/8 

9/6 

6/- 
3/3 
0/- 



1H5GT 7/6 
1L4 2/8 

1UA4 17/6 
1L.A6 18/10 
1LD5 4/- 
1LN5 4/6 
1N8GT 8/6 



1P1 

1P10 

1P11 

I K.i 

134 

135 

1T2 

1T4 

11.4 

1US 

2A7 

2C26 

2D1SC 

2D21 

2X2 

3A4 

SA5 

3B7 

3D6 

SQ4 

3Q3GT 

334 

3V4 

4D1 

5R4GY 

6T4 

5U4G 

5V4G 

5Y3GT 

5Z3 

5Z4 

6'30L2 

g 160 
6A8G 

6AC7 

l)AG5 

0AG7 

liAJii 

6AK5 

0AK6 

DAK8 

SAL-5 

liAM4 

6AM5 

i.AMii 

6AQ0 

8AR6 

6AT6 

6AU6 

6AV6 

6BSG 

6BSG 

BBA6 

6BE6 

6BH6 

6BJ8 

6BQ5 

6B0.7A 

6BR7 

6BR8 

6B37 

6BW6 

8BW7 



4/3 
2/3 
4/- 
3/- 
3/- 
10/9 
8/- 
5/9 



6CD6G 18/- 
SCD7 9/6 



6CH6 
6CW4 
81>1 
6D3 

ape 

6E5 

6F1 

8F6G 

6F6GT 

6F7G 

6F8 

6F12 

6F13 

6F14 

6F15 

6F16 

6F17 

SF18 

8F23 



2/3 
5.6 
5/3 
12/6 
2/9 
7/- 
5/6 
3/- 
3/9 

N9 

5/- 

3 a 



6F33 

6G6 

6H6 

6J5G 

6J5GT 

6J6 

6J7G 

6J7GT 

6K6GT 5/6 

6K7G 1/8 

0K7GT 4/9 

6K8G 
5/8 I 6KSGT 
6/9 



6/6 
24/- 
1/6 
9/6 
3/- 
9/6 
9/6 
3/9 
7/6 
5/- 
5/- 
3/- 
3/9 
25/- 
6/9 
6/8 
12/6 
13/5 
9/8 
10/6 
3/- 
8/8 
2/6 
1/6 
8/9 
4/3 
8/- 
4/6 
II- 



4/9 

s/- 
an 

8/6 

7/- 
4/9 
8/- 

w 

6/6 
7/0 

8/9 

3/9 
5/9 
3/- 
2/6 

5/9 
8/8 
1/9 

u/- 

5/9 
2/ 3 

16/6 
2/8 
3/- 
5/9 

20/- 
3/6 
5/9 
5/6 

12/6 
2/6 

w 

4/3 
5/3 
6/6 

m 
m 

8/3 
8/- 
25/- 

m 

5/- 



3/3 
8/6 
6K25 24/- 
6L1 10/- 
6L5G 12/6 
8L6GT 7/3 
6L7GTM 5/6 
6L18 10/ 
6L19 
6LD3 
8LD13 
SUMO 
6>"7GT 
6P1 



0P25 
61-26 
8P28 
6Q7G 



19/- 
6/6 
6/3 
6/6 

9/3 



9/6 

8/- 

6/9 

5/- 

15/- 

14/6 

7/- 

5/9 

12/8 

5/- 

5/- 



25Z5 7/8 
25Z6GT 8/- 



28D7 

30C1 

30C15 

30C17 

30C18 

30F5 

30FL1 

30FL14 11/- 



6/9 
6/6 
10/- 
11/9 
9/3 
7/3 



8D2 


2/fi 


9BW6 


9/6 


892 


3/- 


9D7 


7/6 


10C1 


9/9 


10C2 


12/- 


10D1 


7/- 


10D2 


11/8 


10F1 


10/- 


10F9 


9/9 


10F13 


9/9 


10LD3 


«/» 


10LD11 9/6 


10P13 


12/- 


10P14 


11/B 


11D3 


17/6 


11D5 


17/6 



aOLl 



5/6 



12/- 
7/6 

5/3 



30L15 10/3 
30L17 11/6 
30P4 
301' 12 
30P16 

30P19 12/- 

30PL1 9/6 

30PL13 10/6 

30PI.14 11/3 

S'S'30PL15 9/8 

33/51 12/6 

3SA5 20/9 

35L6GT 6/- 

35W4 4/8 

35Z3 18/2 

35Z4GT 4/6 

list i« 35Z5GT 5/9 

v.»« J/a "SUA 6/8 

UAO aid jimti 8/- 

"" 413TH 10/- 



AC6PEN4/9 
AOPF.N 

(5) 17/6 
AC/PEN 

(7) 17/- 
AC/SG 22/6 
AC/8G/VM 

12/- 
AC/TH110/- 
AC/TP 18/- 
AC'VPl 12/- 
AOVP212/- 
ATP4 2/3 
AZ1 8/8 



12A3GT16/6 
12AC6 8/6 
12AD6 9/6 
12AE6 8/- 
12AH7 5/- 



10/- 

17/6 

45Z6GT 15/- 



12AT 
12AT7 
12AU6 
12ATJ 



l,1*ITO Tftifl , '**"' l ' v ** *W|- 
"tfl ^'/fi 50A5 »' 1P 

;',„ 50B5 6/6 
|j2 50C5 6/6 
J',? 50CD6G40/9 

12AY6 iV"™? 1 6/- 

12AX7 4/8!»^}i \\'l 

12AT7 9/9!f' "6 

12BA6 5/8 1: 

12BE6 4/9 I L' 

12BH7 6/- I 'A 

12E1 16/9 

12H6GT 1/6 

12.T5GT 2/8 

12J7GT 7/3 

12KS 10/- 

12K7GT 3/6 J0CG 



AZ31 


9/6 


AZ41 


«/6 


Ban 


4/9 


B349 


10/3 


11719 


5/9 


B1.63 


10/6 


CI 


12/6 


CK506 


6/6 


CM 


19/6 


n.33 


11(6 


eve 


2/6 


eves 


10/6 


CV271 


12/6 


UV42H 




CY1 


16/4 


CY1C 


6/6 


CY31 


5/9 


Ul 


1/3 


1)15 


13/6 


D42 


10/6 


l'|>3 


6/- 



F.AK42 7/9 

ebs4 li- 
ma 4/9 

EB91 2/8 

EBC3 20/6 

EBC33 6/- 

EBC41 6/6 

EBOil 6/3 

EBC90 3/6 

EBC91 6/6 

EBFflO 6/9 

BBTOS 7/8 

EBF89 6/9 

EI1L21 10/3 

KC52 4/3 



ELS4 

ELS5 

EI.S6 

E1.91 

E1.9S 

KL360 27/- 

E 1.920 16/4 



6/6 
5/- 
4/9 
5/3 

s:- 

6/6 
67/6 
67/6 
42/- 
42/- 
18/8 
123A7GT6/9 150B2 16/6 



D77 2/8 

DAC32 7/8 

UAF91 8/8 

DAF96 6/- 

DCC90 6/9 

DD4 12/6 

D1>41 10/8 

DDT4 7/6 

r>F.T2ft 7/6 

UF33 8/6 



83V 
B6AS 

90AG 

90AV 



12K9GT 8/8'90CV 
12Q7GT 3/6 90C^_ 



DF6 

DF72 

DF91 

DF96 

DF97 



15/- 
30/- 
2/3 
6/- 
10/- 



9/- 
11/6 
4/3 



6Q7GT 7/9 
6R7G 5/3 
HR7GT 11/- 
68A7 71- 
6SC7 4/9 
68G7 7/9 
68G7GT 4/9 
63H7 3/- 
6S.T7GT 4/8 
68K7GT 4/6 
68L7GT 4/9 
B8N7GT 4/6 
8SQ7 5/- 
68T7 12/6 
6337 2/- 
6U4GT 8/6 
6U5G 
6U7G 
6V6G 
8V6GT 
6X4 



1280? 4/- 

128G7 8/- 

12SH7 8/- 

12S.T7 5/- 

12SK7 3/- 220B 

12SQ7 8/- 3P1 



130C2 5/8 
161 15/- 

185BT 34/11 
S198G 



12SB7 

12Y4 

13D1 

13D3 

14H7 

1487 

18 

19. 



19AQ5 7/3 
19BG6G20/5 
19H1 6/- 



12 / 8 1203A 

10/6 1622 . 

" 2101 



6X5 

HY7G 
6Z5G 



5/- 
71- 
3/6 
5/6 
3/9 
5/3 
12/6 
15/- 
12/6 
5/6 
12/6 



20D1 
20D2 
20F2 
20L1 
20P1 
20P3 
20P4 
20P5 
21AB 



4033 

4687 
10/- 
21/- 

U/6 

14/- 

12/6 9U02 
12/- 9006 
13/- A1834 20/- 
11/6 .AC044 9/- 
6/9 [AC2HL10/6 



10/6 
20/- 
15/- 
15/- 
16/6 
13/- 
11/9 
2/- 
71- 
12/6 
12/8 
15/- 
71/- 
7/6 
10/- 
1/6 
2/9 
4/6 
2/6 



DB730 15/6 
UH63 4/8 
DH76 8/6 
UH77 3/6 
DH81 23/3 
UH101 25/- 
DH10716/U 
DH719 5/9 
DK32 7/6 
DK40 16/6 
DK91 4/- 
1»K92 
DK96 
HI.:;:-: 
DL85 
DL68 

UI.72 
DL75 
1)1.92 
l)L94 

Ll] 'J6 



12/0 
87- 

4/9 
2/3 
4/- 
6/6 
7/3 
4/6 



EC54 

El '70 

BC80 

r.i'i'i 
BOBS 
BCC8] 
F.CC32 
BCC33 29/1 
Ei.::; 21/7 
ECCSft 4/9 
ECC40 10/- 
ECC8 1 3/6 
KCC8'2 4/6 
BOCB3 4/6 
l-'i'i- 1 6/6 
Ei r-5 5/9 
ECC88 8/9 
ECC19911/6 
BC0804 3/9 
KCO807 15/- 
ECF80 7/8 
ECF82 6/8 
ECF88 10/- 
BCF804 24/- 
1.. n, 23/3 
ECHH1 10/- 
ECH38 22/8 
ECH35 6/- 
ECH42 81- 
EPH81 5/9 
ECH83 6/6 
ECU64 9/6 
ECL80 5/8 
ECL82 8/6 
ECL83 10/- 
ECL86 8/- 
EF6 20/8 
EF9 20/6 
EF22 6/6 
BF86 
El' .17 A 
EF39 



EL822 
EMI 
KM 35 
EM 71 
BM80 
EMS J 

BM84 

EMS5 
E.M87 
EN 31 
EMU 
EY81 
BY81 

EYS3 

e ysi 

EV88 
EV87 
EV88 
EV91 
BZ88 
EZ40 

BZ41 

E/sii 

EZ-1 

EZ90 

FC2 

FC4 

FC13 



22/6 
17/9 
12/- 
15/6 
6/3 
7/- 
6/- 
8/9 
7/6 
10/- 
5/6 
5/6 
7/3 
9/3 



5/6 

6> 

3/9 

3/- 

5/3 

5/6 

6/3 

3/9 

4/3 

3 W 
14(6 

8/8 I PCL8S 6/6 
14/6 1'Ll.- 8 
FC13C 17/- IPCL84 
FW4/S00 8/6 PCLS5 
FW4/9008/6IPCLS6 

1 1 r * 



N7S 28,'- 
S108 26/2 
N339 25/- 
P41 3/6 

P61 2/6 

PABC80 6/9 
PCS0 9/9 
PC88 9/- 
PC95 6/9 
PC97 6/9 
PCC84 6/6 
PCC85 6/9 
PCC88 10/6 
PCC89 11/6 
Peci89 9/6 
PCF80 6/6 
PCF82 6,'- 
PCF84 8/6 
PCFSIS 8/3 
PCF801 9/9 
PCF802 10/- 
PCFS05 9/3 
PCFB06 12/9 



RG1'240A 






65/- 


RK34 


7/6 1 


S130 


22/6 


SP4B 


19/6 


3P13C 


12/fl 




SP41 


2/- 




8P42 


12/6 




SP61 


2/- 




S1'25 


BWJS 




T41 


9/- 





T 1)1)2 12/6 



V301 
U33S 

U339 
U403 
VT404 
L'901 
C4020 

VMP4G 11/9 
VMS4B 12/- 
YP2 3/6 

VP2B 9/6 
VP4 14/6 



11/-' 
9/- 
9/6 
9/9 
6/- 

15/- 
6/6 



7/6 
10/- 
10/6 



25A6G 7/6 l AC2PES 



251^ 4/9 
25t"4GT 14/7 
25Y5 7/9 
25Y5G 7/9 
25Z4G 6/8 



11/6 
AC2PES ' 

DD 12/6 
AC5PEX' 

DD 23/3 



8/- 
6/6 
8/9 
5/- 
5/3 
15/- 
30/- 
4/9 
5/- 
6/6 

ni,aio io/6 

DM70 6/- 
DM71 9/9 
1 IW4 3508/8 
l>W4 5008/6 
DY88 6/6 
DYS7 7/6 
E80F 24/- 
ES3F 24/- 
E88CC 18/6 
E180F 19/6 
E3148 1/6 
EASO 1/6 
EA76 8/9 
EAB084 5/9 
EAC91 8/3 



BF40 

EF41 

EF42 

EF50 

EKS4 

EF73 

EF80 

EF83 

F.F85 

BF86 

EF89 

F.F9I 

EF92 

EF97 

EF98 

EF183 

EF1S4 

Ell 91 1 

EKS2 

EIJ2 

El.: is 

EI.34 

EL35 

EL38 

EI.37 

El.41 

F.l.4'2 

BL8I 

El. -3 



3/6 
7/- 
B; 
8/9 

lie 

3/9 
2/6 
8/- 

a- 

4/8 

9/9 
4/6 
6/8 

1/3 
3/- 
8/6 
10/- 
9/9 
7/3 

8/6 

9 '6 
6/9 

3/6 

BM 

D'9 
10/- 

S/9 
12/3 

;/- 

7/9 
8/3 
6/9 



7/6 

8/9 
9/9 1PCL88 12/8 
65/- PES40DD 
7/6 ! 34/- 

8/- PEX45 71- 
14/6 PEN45DD 
10/- 12/- 

14/8 PBS46 4/- 
6/- PES 383 10/3 
PES45S1U1 
10/6 
I-ENA4 7/- 
PES/DD 

4020 17/6 
PFL20014/6 
PL33 9/- 
PL86 
PL33 
FLS1 
PT.>2 
PL8S 
PL84 
P1.500 



OTIC 
lib' 50 

ozse 

OZ89 
GZ8S 

GZ34 

GZ37 

U30 

HABC809/3 

HL2 7/6 

HL13C 4/- 

H1.23 12/6 

HL23DD 5/- 

Hl.il 3/9 

HL41DD12/8 

1IM2DDI2/6 

HLl3:i['l'8/8 

HN30B 26/- 

HVR2 8/9 

HVR2A 8/9 

1 m 5/6 

1W4/360 5/6 

1W4 aim HI- P.MS4 

KBC32 20/5 'PT15 



TDD4 
TH4B 
TH2K 
TH30C 14/6 
TH41 15/6 
TH233 6/9 
TP22 5/- 
TP25 5/- 
TP2I120 7/6 
TYS8F 11/8 
1." ABC80 5/8 
OAF42 71- 
b'B41 10/6 
LBC41 6/3 
VBC81 6/3 
1.BF80 5/6 
TBFSH 6/3 
1BL21 10/9 
UCB2 6/3 
T7CC84 8/- 
UCC86 
I'CFSO 
UCH21 
UCH42 
L'CUSl 
LCL82 
OCL83. 
CF41 



9/- 
16/- 
6/9 
5/3 



KK33 12/8 
KL35 11/6 
KLU! 21/' 



KT2 

KT8 

KT32 

KT330 

KTSi'. 

KT-il 

KT44 

KT61 

KTfi:' 

KT66 

KT74 

KT7S 



5/- 
15/- 
4/9 
6/- 



PX4 
PY31 
PY32 
PY33 

I'Y8il 
PY81 
PY82 



29/1 ' PY83 
6/9 



5/- 
6/9 
3/9 

12/3 



PY.sno 

PY801 
PZ30 
QP21 
12/6 QP22B 12/6 
7/6 QQVOS.'IO 
28/- 35'- 

KTW61 4/8 |Q87520 10/6 
KTW69 5/6 ' QS150/159/6 
KTW61 5/8 ■ Rio 15/- 
KTZ41 5/6 K 12 5/6 

8/9 i V. 16 29/- 
5/9 K17 i',/6 

9/6 R18 9/6 

9/6 ftU 6/9 

9/8 ' R32 7/6 



US 

LSI 52 
LN309 
LS319 
LP2 



L1'4V 

UFS0 

CF85 

UFSH 

UFS9 

BX41 

LL46 

UL84 

OK4 

UM34 

UM80 

URIC 

DTJ5 

UUfi 

tX'7 

L'U8 

UU9 

r;ui2 
i. v i s 

L'Y21 

UY41 

0Y8S 

1.10 

U12/14 

U10 

U17 

U 18/20 

DM 

1:22 

U2S 

U26 

L"31 

C33 

U35 

l!37 

C4S 



("76 
U78 
U101 

rn.7 

L'191 
i:231 
U2f«l 
C282 



6/8 
8/3 
S/- 
8/- 
6/6 
7/3 
9/- 
6/9 
4/9 
6/3 
6/9 
9/- 
5/6 
71- 
8/6 
5/6 
17/6 
17/6 
8/3 
6/6 
7/- 
11/- 
U/- 
14/- 
5/6 
4/3 
10/3 
9/- 
67- 
4/9 
9/- 
7/6 
15/- 
5/- 
6/6 
48/6 
5/9 
8/6 
7/6 
6/6 
13/6 
16/8 
29/- 
15/6 
8/6 
4/9 
4/9 
4/6 
3/8 
19/6 
17/6 
9/6 
9/- 
8/9 
12/3 



VIM A 

VP4B 

VP13C 
VKM 

VP41 
VP138 
VR75 
VR105 

VR160 

VT61A 

VT601 

VU111 

YC120 10/- 

Vi:i20A10/- 

VI) 133 7/- 

W21 

W42 

W61H 

W63 

W76 



14/6 

12/- 



6/- 
9/9 
21/- 
5/6 
4/9 
7/- 
3/- 
5/- 



GD14 10/- 
GET103 71- 
GET104 10/- 
UET10617/8 
GF.T1U12/- 
GET113 6/9 
GET114 6/6 
OET11617/- 
OKT878 9/3 
1 ; 1:1.174 9/6 

GExaa 3/6 

GEX33 3/- 

IIEX36 10/- 
GEX45 8/6 
GEX64 11/8 
GEX6I1 15/- 
11 AT 1 00 7/9 
'MAT101 8/8 
MAT120 7/9 
MAT121 8/6 
OA5 6/- 

OA10 



W77 

TTSIM 

W101 

W107 

"SV729 

X14 

X18 

.V24 

X41 

X61 

X63 

X64 

X'35 

XS6 

XT6M 

X78 

X79 

X81M 

X101 

XI 09 
XI 18 
X119 

X142 

Yl.i:i 

1 65 

Z63 

/.I'll) 

Z77 

Z729 

Z749 

Z759 



B- 

12/- 

24/6 I 

10/6! 

3/6 

2/6 

5/9 

26/2 

10/6 

17/6 

7/9 

8/- 

16/6 

10/- 

6/- 

5/9 

5/6 

5/8 

7/3 

8/6 

26/2 

27/- 

29/1 

29/1 

26/- 

9/9 

6/6 

8/- 

5/- 

5/- 

4/6 

7/3 

3/- 

6/6 

9/3 

36/- 



OA70 
OA73 
OA79 
OA81 

OA83 

OA.sa 

OA90 
OA91 
OA95 
OA200 
OA211 13/8 
OAZ200W/8 
OAZ203 9/8 
OAZ204 9/6 
OAZ210 7/6 
OC16W 35/- 
OC19 25/- 



3/. 

:■:/. 
3/- 
3/- 
3/- 

t 
XI- 
3/6 
5/- 



OC22 
OC23 
OC25 

ocse 

OC28 
OC29 
0C8S 
OO86 

Ol-41 
OC42 
OC43 
OC44 



23/- 
57/- 
12/- 

8/- 
23/- 
16/6 

6/6 
21/6 

8/- 

8/8 
12/6 

4/9 



Transistors 
and diode* 
AA120 4/6 
AA129 
AC107 
AC113 
AC I 14 
AC127 

AD140 25/- 
AF102 27/6 
AF114 11/- 
AF11S 10/6 
AF1M 10/- 
AF117 
AF118 
AF124 
AF125 
AF126 
AF127 
AF188 27/6 
AFZ12 26/6 
BYZ13 11/6 
GD3 6/6 
GD6 5/6 



4/6 
14/0 
8/- 
8/- 
9/G 



5/6 
20/- 
11/- 
10/6 
10/- 

9/6 



OC44PM 8/3 


OC45 




OC46M 


8/- 


oceo 


22/6 


01:66 


23/- 


OL70 


K/U 


Oi"71 


3/B 


0072 


8/- 


Ol'73 


16/- 


O074 


•</- 


OR7S 


8/- 


OC70 


8/8 


OC77 


13/- 


OC'78 


8/- 


Ol'-l 


4/- 


OC81D 


4/- 


OC81M 


4/- 


0088 


1U/- 


in 83 


6/- 


OC84 


8/- 


OO 139 


12/- 


Of) 40 


19/- 


OC170 


8/6 


00171 


8/- 



OC200 10/6 
OC201 29/- 
OC203 14/- 
00204 10/6 
OC206 10/8 
OOP71 27/6 
ORP12 12/6 
T82 12/6 

TS3 15/- 

V10. 18A 12/- 
XA103 18/- 



WE REQUIRE FOR PROMPT CASH SETTLEMENT ALL TYPES OF VALVES, LOOSE OR BOXED, BUT MUST BE NEW 

METALl 

14A97 

18RA.: 

ELECTROLYTICS. 

100: 

Midget 1 

EXPRESS POSTAL SERVICE! ALL ORDERS DESPATCHED SAME DAY AS RECEIVED 

Xerou of liu=inc«--— Cash with order oniv. PonPackinc Od. per item. Orders over «5 post free. So C.O.D. All orders i-icsred daj of rnceipt. Any parcel Insured 
against damage in transit for Gd. extra. We are open for personal shoppers 9.00—5 p.m. Sati. 9.00—1 p.m. Complete Bat 03 modern and obsolete valves, resistor*. 

condensers, transformers, potentiometers, microphones, etc. with terms of uusinv.-? •'«•.. Pi-.-a.-e ../I'l/iiro lor an; ii r ~ ;,<:■;■ list .-..: viih ».A.E 



Tlffa+hJa±. 



1014 PRACTICAL WIRELESS April, 1966 

niiiiiiimiimiiiiiiiiiiiiiiiiiiiimiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiM 

™__=^ Heathkit models offer 

outstanding performance plus 
highest quality — at lowest cost 

Anyone can build a Heathkit model. The easy-to-follow instruction manual issued wi 
each kit-set shows you how. You will be proud of the professional appearance and performan 
of your finished model. 

A KIT FOR EVERY INTEREST . . . FOR HOME, WORKSHOP, SERVICE & TEST DEPT. 



t 

ce 



TEST INSTRUMENTS 




IB 



3" PORTABLE 'SCOPE. OS-2 With 
improved performance and modern 
styling. 'Y' bandwidth 2 c/s-3 mc/s. 
Automatic Lock-in sync. Mumetal C.R.T. 
shield. P.C. Board. Size 5" x 7" x 12" 
deep. Weight 9Jlb. 
£30.8.0 Assembled £22. I 8.0 Kit 

Sin. OSCILLOSCOPE Model I0-I2U. 
Laboratory quality at utility oscilloscope 
price. Wide band amplifiers essential (or 
T.V. servicing. F.M. alignment, etc. T/B 
covers 10 c/s-500 kc.'s in 5 ranges. 

£45.15.0 Assembled /JC 17 A Kl[ 



OE-LUXE TRANSISTOR TESTER, IM-30U 

Provides complete d.c. analysis of PNP, NPN transistors and 

diodes. 

£35.10.0 Assembled £24.18.0 Kit 

REGULATED POWER SUPPLY Model IP-20U. Transistor- 
iced, 0.5-SO v. D.C. Up to 1.5 amps. Compact: 9$ x 6{ x 1 1 in. 
£47.8.0 Assembled £35.8.0 Kit 

44* VALVE VOLTMETER. Model V-7A. The world's 
best selling VTVM. Measures up to 1.500 volts 
(d.c. and r.m.s.) and 4.000 pk. to pk. Res. 0.1 II 
1.000 Mil. Centre zero dB scale, d.c. input resistance 
1 1 MSI. 4iin. meter. Complete with test prods, leads 
and standardising battery. / I "5 I ft A •.• , 

£19.18.6 Assembled EU.IO.OK.t 

DE-LUXE 6in. VALVE VOLTMETER. Model 
IM-I3U. Similar spec, to model V-7A but with im- 
proved accuracy. Larger meter. Unique gimbal mount. V-7A 
£26.18.0 Assembled £ | ft. | ft.Q Kit 



SINE'SO. GENERATOR. Model 
IG-82U. Freq. range: 20 c/s — I 
Mc/s in 5 bands. Simultaneous sine 
and square wave outputs. 

£36.10.0 Assembled£24 10 Kit 





IG-82U 



HARMONIC DISTORTION METER. Model IM-I2U. 
Fre. cov.: 20-20.000 c.s. 

£34.0.0 Assembled £24. | 5.Q Kit 

TV ALIGNMENT GENERATOR. Model HFW-I. Covers 

3.6 to 220 Mc,s fundamentals. jfTJ Ift fl tr 

£47.10.0 Assembled U/.IO.VM 

RF SIGNAL GENERATOR. Model RF-IU. Up to 100 Mc's 
fundamental, 200 Mc,.s harmonics. Up to 100 mV output on all 
bands. £19.18.0 Assembled £|3 8 0Kit 

MULTIMETER. Model MM-IU. Ranges: 0-1.5 v. to 1.500 v. 

a.e. and d.c; ISOuA to I5A d.c; 0.2JJ to 20MO. 4Jin. 50y.A meter. 

£18.1 1.6 Assembled £| 2. 1 8.0 Kit 

A wide range of other test instruments available. 

HI-FI DEMONSTRATIONS & EXHIBITION 

Concurrent with the Audio Fair. 
The Grand Hotel, Southampton Row, London. 

II a.m.-9 p.m; (8 p.m. Sun.) April 14-17 inclusive. 





AMATEUR EQUIPMENT 

AMATEUR TRANSMITTER. Model DX-I00U. Covers 
all amateur bands I60-I0M. ISO w. d.c. input, self contained 
with power supply. Modulator, VFO fTQ I ft 

Assembled £104.15.0 *•' '• ■ w,w M 

AMATEUR TRANSMITTER 
Model DX-40U. Covers 80-10 m. 
Power inputs 75 w. C.W., 60 w. 
peak C.C phone. Output 40 w. to 
aerial. Prov. for VFO. 

£33.19.0 Kit 

Assembled £45.8.0 



DX-40U 

AMATEUR BANDS 
RECEIVER, RA-I 

Outstanding performance at low 
cost. Covers the amateur bands e 
from 160-10 metres. Half lattice I 
filter. Signal strength meter. * 
£52.10.0 £39 A. A K ,. 

Assembled MT.O.O K,t 

Other kits in the amateur range include: SSB Adaptor SB-I0U 
£39.5.0. Variable freq. Oscillator. VF-IU £10.17.6. Balun 
Coil Units B-IU £4.15.6. Grid-Dip Meter GD-IU £10.19.6. 
Q Multiplier QPM-I £8.10.0. Reflected Power Meter HM- 
IIU £8.5.0. Receiver, RG.I £39.16.0. 

SPEAKER SYSTEMS 

BERKELEY Slim-line LOUDSPEAKER 
SYSTEM 

+Now from Heathkit, a loudspeaker kit with a 
fully finished walnut cabinet, -fa A 2 speaker 
system. -f( Modern, slim-line styling. ^ 30 c s 
to 17 kc.s. ■*• Only 7J" thick, -fr Use it hori- 
zontally or vertically. -£• Stand it on the floor or 
in your bookshelf. 
Berkeley , "3.0.0 Assembled £ 1 8 . 1 0.0 Kit 

COTS WOLD STANDARD MODEL 

Acoustically designed enclosure "in the "white" 26 x 23 x 1 5 j-in.. 
1 2.i n. bass speaker, elliptical middle speaker. 2in. pressure unit. 
Covers 30-20,000 c/s. Complete kit with all controls. 

£25.12.0 Kit 



MFS SYSTEM (illustrated) 

A minimum floor space model for the smaller 
room. 26in. high x I6iin. x I4in. deep. Similar 
performance to standard model. £25 12 K't 



SSU-I SYSTEM 

A practical solution to the problem of a 
moderately priced speaker suitable for Stereo 
Mono amplifiers where the equipment has to 
be compact. Two speakers, balance control, 
ducted port reflex cabinet. 

Incl. P.T. £11 17 6 Kit 

CI I.I /.O (i^ , egs) 

Set of 4 legs (7" or 15") 14 6 extra. 






DAYSTROM LTD 



5 Dept. PW4 GLOUCESTER, ENGLAND 



April, 1966 



PRACTICAL WIRELESS 



1015 



MODELS FOR HOME, TEST AND WORKSHOP. 

BRITISH HEATHKIT MODELS USE BRITISH COMPONENTS 

HI-FI AMPLIFIERS 



HeM±hJU±. 



DE-LUXE ALL TRANSISTOR STEREO AMPLIFIER AA-22U. 

A quality British transistor amplifier with high power (20 -f- 20W) at 
a reasonable cost, capable of delivering full power at all frequencies 
in the audio band. Handsome fully finished walnut veneered cabinet 
available. Professional slim-line styling. Send for full specification. 
Kit (less cabinet) £39.10.0 Cabinet £2.5.0. Accessories for panel mount- 
ing £1.18.0. 







t t m ^umt^n A 



6W DE-LUXE STEREO AMPLIFIER. Model S-33H. An 

inexpensive scereo amplifier with high sensitivity. Suitable for 
use with Decca Deram cartridge. £ I C 11 A i/- 

£21.7.6 Assembled H3. I /.O KM 

TAPE RECORD/REPLAY AMPLIFIER KITS. Will operate 
with most tape decks. Send for details. 
TA-IM (Mono). 19.18.0 Kit. TA-IS (Stereo). £25.10.0 Kit. 
STEREO CONTROL UNIT. Model USC-I. Ideal for use with 
MA- 1 2 amplifiers. Kit £19.10.0. Assembled £26.10.0. 

6W STEREO AMPLIFIER 
Model S-33. 3 w;ch. Inputs for 
radio, tape and gram. Stereo Mono 
ganged controls. Sensitivity 200m V. 
£18.18.0 Assembled/ j 3 J £ ^ 




TRANSISTOR MIXER, Model TM-I. A must for the Tape 
enthusiast. 4 channels, Battery driven. / I I I A A vi~ 

£16.17.6 Assembled 1 1 I . I O.O Kit 

5W HI-FI MONO AMPLIFIER. Model MA-5. A low priced 
amplifier based on the S-33. Printed circuit construction makes 
it easy to build. £|fl I O A «:, 

£15.10.0 Assembled CIU.IT.OK.it 

HI-FI MONO POWER AMPLIFIER. Model MA-12. Ideal 
for use with Models USC-I and UMC-I. 0.1 THD at I0W. Wide 
frequency range. £15.18.0 Assembled £\ I I O A . ... 

I8W STEREO AMPLIFIER. lll.IO.WWt 

Model S-99. Ganged controls. 
Stereo/Mono gram, radio and tape 
record inputs. PB selection. 
£38.9.6 Assembled £28.9.6 Kit 



S-33 



A range of R 'players, T I Decks available. 

Send for full spec, of any model 

Prices quoted are Mail Order and include free delivery in UK. 




S-99 





TRANSISTOR RECEIVERS 

"OXFORD" LUXURY TRANSISTOR 
DUAL WAVEBAND RECEIVER. 

The ideal domestic or personal portable 
receiver. 10 Semi-conductors. Solid leather 
case. Send for full details. £|4Jg.O Kit 

6 TRANSISTOR PORTABLE. Model 
UXR-I. Prealigned I.F. transformers. 
Printed circuit, 7in. x 4in. high flux speaker. 
Real hide case. Very easy to build. 

lndPT £12.11.0 ku 



"MOHICAN" GENERAL COVERAGE 
RECEIVER. Model GC-IU. Excellent 
portable or general purpose receiver for 
"amateur" or short wave listening. See full 
spec, leaflets. (XJ \f L K| 

Assembled £45.17.6 tJ/.l/.O Kit 




PA/GUITAR AMPLIFIERS 

Model PA-I (similar to PA-2 illus- 
tration) 50 watt output. Two 
12" L.S. Variable tremolo. 4 
inputs. £54 | 5 Kit 

Assembled £74 fc "*^' • •*•»» 
legs or castors available (extras). 
Model PA-2 (illustrated). 
Starmaker 33. All transistor 
20 watt output, two 12* L.S. 
Variable tremolo, 4 inputs. 
Compact size. 
Assembled £59.10.0 (AA [ Q,0 

Legs or castors available (extras). 
50 watt Power Amp. MA-50 




Assembled £27.18.0 



£19.18.0 Kit 




HI-FI TUNERS 

Model FM-4U. Tuning range 
88-108 Mc/s. Tuning unit (FMT- 
4U) with 10.7 Mc/s. I.F. (£2.15.0 
incl. P.T.). I.F. Amp. (FMA-4U) 
complete with cabinet and valves 
(£.3.13.0). Total £|$.8.0 Kit 

Assembly can be arranged. FM-4U 

AM FM TUNER. Covers FM 88-108 Mc/s. A.M. 16-50. 200-550, 
900-2.000 m. Tuning heart (£4.13.6 incl. P.T.), and I.F. Amp. 
(£22.11.6). Total £27 5 Kit 

Send for leaflets. Assembly can be arranged. mtmtm ,-■>■• 

EQUIPMENT CABINETS 

A large range, in kit form or assembled 
and finished, available to meet most needs. 
Illustrated details on request. 

Prices from £8.8.0 to £46.4.0 

SPEAKERS FOR YOUR OWN ENCLOSURE 
12" Heavy-duty Bass (Fane 122/12) £7.7.0. 
2* Tweeter (Fane 301) £3.1.6. 

(both as used in the Cotswold systems). 
8" Goodman's General Purpose G8 £1.8.6. 
Two Speakers + Cross-over, System SCM-I. 

(As used in model SSU-I) with details for enclosure £5.5.0. 

ELECTRONIC WORKSHOP KIT. Model EW-I. An out- 
standing experimental kit for children. £7.13.6 incl. P.T. 

A WIDE RANGE OF BOOKS ON ELECTRONICS AND 
RADIO. PLEASE SEND FOR LISTS AND PRICES. 

American Heath Catalogue, price lists in £ s. d. and details of 

direct delivery scheme sent for I/- p. paid. 




Welcome to our 

LONDON HEATHKIT CENTRE. 

We have opened a showroom and retail stores 
at 233 Tottenham Court Road. 



To DAYSTROM LTD. Dept. P.W.-4, GLOUCESTER, ENG. 

Please send me FREE BRITISH CATALOGUE (Yes'No) Full details 
of model(s). Amateur Brochure (Yes/No), American Catalogue 1/- 

(Yes/No), Instrument Brochure (Yes/No) 

NAME , 



= WHEN YOU ARE IN TOWN. WE HOPE g ADDRESS 
= THAT YOU WILL VISIT US THERE 



1016 



PRACTICAL WIRELESS 



April, 1966 




Offer the Finest Value and 

HOME CONSTRUCTORS 

I We comider our construction parcels to be the finest value on the home construe- 1 
tor market. If on receipt you feel not competent to build the set, you may return I 
it as received within 7 days when the sum paid will be refunded less postage. I 



THE "SKY ROVER" RANGE 

GENERAL SPECIFICATION 

7 transistor plus 2 diode superhet. 6 waveband portable 
receiver. Operating- from lour 1.5 v. torch batteries. 
The SKYROVER and SKYROVER DE LUXE cover the 
full Medium Waveband and Short Waveband 31-94 M 
and also 4 separate switched band-spread ranges. 13M, 
16M. 19M and 25M. with Band Spread Tuning for accu- 
rate Station Selection. The coil pack and tuning heart 
is completely factory assembled, wired and tested. 
The remaining assembly can be completed In under 
three hours from our easy to follow stage by stage 
instructions. 



1 : "" ' m—imi 




A simple additional circuit 
provides coverage of Che 
U00/1950M. band (including 
1500 M. Light programme). 
All components and de- 
tailed construction data. 

Only 10- extra ££ 

This conversion is suitable 
for both models that have 
already been constructed. 



Data for Receiver 2/6 extra. 
Refunded if you purchase the 
parcel. Four U2 batteries. 3/4. 
extra. All components available 
separately. 



NEW— The SKYROVER Mk 111 



\ow supplied with redesigned cabinet, cdftewlsc 
controls, hluek and chrome plastic cabinet. 
Size 10 x 61 x 31in. with carrying handle, 4>o 1QC Post 
tan now be built for *"»■ ■ *»•'» 5/- 

il-l*. Terms: 27/- <iep. and 11 months at 15/9. Total 
H.I\ Price £10.0.3. 

NEW— The SKYROVER DE LUXE 

Tone Control Circuit Is Incorporated with separate 
Control. In a wood cabinet, size Ut x 61 x 3ln., covered 
with a washable material with plastic trim and carrying 
handle. Car aerial socket fitted. 

C an now be built for II.P. Terms: 33/- dep. 

Post 5/- -Ifi 1QC anil II mths. at 19/2- 

X.IU.I3.0 Total U.P.P. £12.3.10 




The Very Latest MAGNAVOX- 
COLLARO 363 TAPE DECKS 

! 3 speed model — II. 31. 7) l.p.s.. available with either » 
track or J track heads. Features Include: pause control: 
digital counter: fast forward and rewind: new 4 pole fully 
screened Induction motor: Interlocking keys. Size of top 
plate 13i x 11 x 5,'in. deep below unit plate. For 200/250v. 
A.C. mains. 50 o.p.s. operation. New. unused and fully 
guaranteed. 

LASKY'S PRICE with 1 track CIA 10 c / rrla £ e 
heads * • "• * *»■*» and packing 

LASKY'S PRICE wl h th a - 1 F ack £13.9.6 7,6e)tCra 



SPECIAL for OVERSEAS C t STO.MERS— the new Magnavox-Collaro 363 Deck for 110/125v. 
60_or_60 c.p.s. mains nowjtvallable. prices as above. Post to any_part_of the World. 35/- 

SPECIAL PURCHASE! 7 TRANSISTOR RAD.O CHASSIS 



Superhet chassis, fully i.uill — l<y lafOOM British maim, 
-ivlng 900 m/v* push-pull "uip.ii - :: I.K. ntiaffrir 

bands— 300 S80U -mi r.'im -J' M md ivttaaed band 

volume control on/off mriteh. inning -llnl sad 
dimension*— 7ta. x 4;in. \ 8in. Abwlateli pomplete tx 

LASKY'S PRICE 



69/6 



.;.'-. 



■ piii.i -I lr. .ill. i ..•- I NfwmUfcM trnn- 

ferrltc rtxt uerial. Coven (nil. long and OMdlMn wave* 

MUM iLoxerahouix). Ilia. -i>«-aker: Btttdi 

lien DM atrial wokM. I a IB] W battery. Overall 

i'pl 101 i-nl ita, 

.- • ■ i ■ ■ i . > -ii.li-ii battery I'l'O. 8/9 or ri'7, 8/3 extra. 



TRANSISTORS new and guaranteed 

GET 81. GET SS. GET S«i. 8/8: *7tfA. "~*P. 
8/6; OC4o. OC71. 0C81D, 4/8; OC44, OC70. 
OC78, 0081 (match pair 10/6). 5/8; Al'117. 
0078.00200, 6/8;OC42. OC43, Oi'7:i. OG82D. 7/B. 
OC201. 00204. 15/-; OC20.V OC800. 1919: 
OC28 84/6. 



TRANSFILTERS BY BRUSH CRYSTAL CO 
TO- 01 B 4«I8 kc/». i '.' ItcK 
TO— OlD 470 KO/a t 2 koM. 
TO — 08B «M ko/a, 4. I kc/B. 

TO— OaD 470 kc/9. ± l ke/t. 

TF-OlB 485 kc.M. -h 9 ke/.i. 
TP— OlD 470 fca/a, ± g ka/«. 



7/6 m 

Post ltd. 




B.S.R. 



AUTOCHANGERS— BRAND NEW 
AT LOWEST EV£R PRICES 



Brand new and fully guaranteed— complete with cartridge 
and stylus. 

UAH 4 speed mains model M £4. 9. a 

UA16 4 speed mains model £4.19.6 

UA16 9v. battery model £5.19.6 

UA20 4 speed mains model £5.19.6 

Add 5/- carrlago and packlnir on each. 



GARRARD AUTOCHANGERS 



Auto-Slim Mono £4 19 

AT8 Mono £8 19 

AT6 Stereo £9 9 

3000I.M with stereo cartridge. . . . £8 8 

SP2S Mono £9 19 

BP85 Bteteo £10 19 



AT'10 »•« partridge . ., £10 19 

AT0 lem oartridfs *19 19 

A3H le.« cartridge £9 14 

AKlOO with 008 cartridge. £6 8 

A8U00 with 008 cnrlrlilKe £7 7 

Pontage on all above 8/- 



SPECIAL OFFER: GARRARD AT5 AUTOCHANGERS 



4*peetl mains model — brand no* 

LASKY'S PRICE 



and fully guaranteed 

with mono etyttal 

cartridge 



£5.19.6 



Witt stereo £/> Q e Port 




The "REALISTIC" Seven 

■k 7-Transistor Superhet. ■*■ 350 milliwatt 
output into 4in. high flux speaker. 
•*• All components mounted on a single 
printed circuit 
board. * Full medi- 
um and long wave 
cover. •*■ Plastic 
cabinet with carry- 
ing handle. size 
7 x 10 x 3 t in.. Blue/ 
Grey or all Grey. i-j-i_ 
■*• Socket for cai 
aerial. • I . F . 
frequency 470 Kc/s. 
+ Kerrlte rod 
internal aerial. Operates from PP9 or 
similar battery. *• Full data supplied. 
All coils and I.F.'s etc. fully wound ready 
for Immediate assembly. An outstanding 
receiver. ^ r tf\ * 

Can be built for £5.19.0 
Post 4/6. mtmmm^wmm 

PP9 Batt. 3/9. Data and Instructions sep- 
arately 2/6. Refunded if you purchase the 
parcel. All parts sold separately. 

REALISTIC Seven DE LUXE 

With the same specifications as standard 
model — PLUS a superior wood cabinet 
in contemporary styling with full vision 
circular dial. QNLy £-| EXTRA 



INTERNATIONAL TAPE 

Famous American Brand — Fnllf Guaranteed 

Sto. Mcwagc tape. lOOtt t 8 

Sin. Message tape. 889ft 4 11 

:iin. Me-ssage tane. 300ft 7 6 

lib. Triple plav, flOOft., Mvlar base 15 

Triplepfey ,900ft.. Mylar base 17 8 

Double play. 1.800ft., Mvlar base .... 16 



Ha. 

9 In. 



Long p!av. 900ft.. Acetate base 

Standard play, liOOft.. PVC base 8 

Triple play, 1,800ft., Mvlar base 35 

5}ln. Double play. 1.800ft,. Mylar base 28 

,'. Jin. Lons play, 1.800ft. Acetatebase IS 

9Jln. Standard plav, SflOft. PVC ba^e 11 

5 Jin. Long play. 1 ,800ft .. Mylar base ...... 16 

Ojln. Triple play, a.400ft.. Mylar ba« 46 

Vin. Standard play. 1.800ft.. Acetate ba=e.. 10 

Tin. Standard play, 1.800ft. Mvlar base .. 12 

7iu. I».ng pb», l.ROfut., Mvlar iMua 19 

7lu. OanMe play, 3.400tU Mvlar raise .... 26 

Ma. I>mg plav. l.sdOft.. Ar^'ale hose 15 

7ln. Tripi- play. :t,i;n»it„ Mylar bace 68 

P. A P. 1 1- extra per reel. 4 reels ann over Post Vr, 



Mn. 



SINCLAIR MINIATURES 



We stock the complete range of 
Super-miniature Kits. 

THE MICRO-6 pocket radio 

THE SI.IMI.INK pocket radio 

THE MICKO-I-'M tuner/receiver . 

THE X-20 Amplifier 

Ready built and tested 

Till-; x-io Amplifier 

Ready built and tested 

See our Practical wireless November 
tisement for details. 



59/6 

49/6 

. £5.19-6 

. .£7.10.6 
. . . i'9. 19.6 
.£5.19.6 
...£6.19.6 
65ad(*r- 



U.H.F. TUNERS 

Only a few available. Complete 
with PC86 and PC88 valves. We 
regret no circuit or data is avail- 
able. Knobs included, 

LASKY'S PRICE 59/6 

Post 2/6. 

GORLER UT 340 FM/VHF 
TUNING HEART 

Permeability tunes — covering 87 to 108MC/S. 
For use with one ECC85 valve. In metal case, 
size 3 x 2! x lj in. Circuit supplied. 

LASKY'S PRICE 15/11 

ECC85 valve 9/- extra. Post 21- 



LASKY'S FOR D.I.Y. CONSTRUCTION BARGAINS 



April, 1966 



PRACTICAL WIRELESS 



1017 



Service in Great Britain to both 

& HI-FI ENTHUSIASTS 

TAPE RECORDERS • RECORD PLAYERS • AMPLIFIERS, ETC. 
COMPLETE MONO/STEREO SYSTEMS TO YOUR SPEC. 

NEW COMMUNICATION 

RECEIVERS 

MODEL KT 320 KIT 




■*upplled in sub-assemblies for easy building. Covers 
range from 540 Kc/s to 30 Mc's. Ham Band is pro- 
vided with a scale lor direct reading and can also be 
band spread. 9 valves, facilities: A.N.L., A.V.C. and 
M.V.C. Q-Multiplier also serves as B.F.O. H.F. stage 
und two I.F. stages ensure high sensitivity and 
selectivity (all colls and I.F.'s are supplied pre- 
uligued). 2 Aerial Sockets, Stand-by position for 
use with a transmitter. 8 meter fitted. 200-2SOV. 
A.C. mains. 8teei cabinet, grey crackle finish. Size 
IS x 8 x 10m. Dial 12 x 4in- All parts new and rally 
guaranteed. Complete with full construction data 
and operating manual. 

LASKYS PRICE 25GNS.^ 

Alio available ready built and tested 29 gna. 
B.F. Terms available. 




MODEL HE80 



Covers full medium waveband and 1.6-4.4. Mc/a. 
4.5-11.0 Mc/s and 11.0-3.0 Mc/s. in separate switched 
band spread ranges. Two aerials are fitted, an 
internal loop and external telescopic Controls 
include: B.F.O. Sensitivity, C.W., A.H.L, tone 
-witch, receive/stand-by, S meter. Easy to read 
illuminated dial with logging scale. For 200/250 v. 
A.C. 4 valves pins rectifier. Fitted with internal 
speaker and socket for phones or external speaker. 
Complete with rail instruction manual. Cabinet size 
13J x 8) x 5$ in. 

LASKYS PRICE 20 GNS. "ft 

H.P. Terms £5 dep. and 11 monthly payments at 

Cl.14.0. Tot al H.P.P. £28.14.0 . 

1 14-valve super sensitive 
mication receiver. 
Freq. range 540 Kc/s— 30 Mc/s. and 144-146 Mc/s. 
Dual conversion on 2 metres, with extra R.F. stage. 
Single R.F. stage, two I.F. stages on all other bands. 
B.F.O. and Q-multiplier circuits. Improved A.&..L. 
and voltage regulated powerpack. "S" meter 
band spread on amateur bands, large illuminated 
dial with logging scale. All controls fitted. Output, 
for speaker and phones. Valve line-up: 4 x 6AQS, 
3 x HBA'i. 2 x 6BE6. 1 x 6BL8. 6AL5, 6AQ5, 6CA4 
and OA2. Steel case 17 x 7$ x lOin. For 20 0/380* . 
A.C. mains. Brand new with full instruction manna]. 
No Kits available. 

LASKYS PRICE 59 GNS. ^ 

H.P. Terms £12.19.0 dep. and 11 monthly payments 

o l £4.18.0. Total H. P J. £66.1 7.0. 

STILL A FEW AVAILABLE 
Fully built and guaranteed 

MODEL HE30 — LASKY'S PBICE 33 GSS. 

MODEL HE40 — LASKY'3 FBTCE 18J GNS. 

H.P. Terms available. 




LasktTs 

RADIO 



THE LATEST "KUBA" 

IMPORTED AM FM 

STEREO RADIOGRAM 

CHASSIS 



Long, medium and short waveband co ver- 
age plus VHF/FM. Piano key wave-cha nge. 
Separate flywheel tuning on AM and I'M 
Bas3, treble and balance controls. Magic-eyo 
tuning indicator, b'erritc rod aerial. The 
very latest printed circuitry. Provision 
5 valves— line up: ECC85, ECHS01, ECC*3. iiLX80, EAF501. Full vision tuning 
i-rall UiiriL-nslona: 21 s fi* X Sin. Made to the very highest standards. 



LASKYS PRICE 2B\ GNS. 



Carriage 6c insurance 12/6 extra. 



TRANSISTOR POCKET RADIOS 

IDEAL GIFTS - AH supplied complete with personal earpiece, battery and 

carrying case. Fully guaranteed— ready to use. POST FREE. 

nrtV'C O TDAMCICTnD ln attractive plastic case. Size only 4in. x 

BUT O / IKANOiaiUK ojtn. x Jin. Fitted 2Jin. speaker. Socket for 

personal earpiece. Uses FP3 battery. 

Tunable over full medium waveband. 




LASKY'S PRICE 35/- 



BOY'S 4 TRANSISTOR MODEL|.ASKY'S PRICE 45/- 
6 TRANSISTOR MODEL 

Fully bnilt m plastic case, 4in. x 2|in. x lin. with 2Jin. speaker,! a (ll/l/tft nniPr C *"\ /^ 
Uses single PP3 type battery. Tunable over full medium wave-[_flj^ J Jj f |\Iot 0«7/0 



band. 

2 Waveband (Long and Medium) ModeL Size 5 x 31 x liin. 

Cream/black plastic case. Including earpiece and carrying case. 



LASKY'S PRICE 89/6 



THE "TRANSWAVE" de luxe two waveband radio 

8 Sony transistors give super sensitive reception over the full Med. and Long wavebands. Internal ferrite 
and detachable chrome telescopic aerials. 2J' p.m. speaker. Smart 
black plastic cabinet with metal trim— size 6| x 3i x liin. Uses 3 
pen light batteries. Complete with leather case and shoulder 
strap, earpiece and batteries. Post 2/6. 



LASKY'S PRICE 95/- 



2 WONDERFUL SETS FROM THE U.S.S.R. 
THE "SELGA" 7 transistor radio 

High sensitivity circuit gives excellent reception over full Med. 
waveband and powerful volume. P.M. speaker. Uses PP3 
type battery. Black and Ivory plastic cabinet size 7 x 4 x 2in. 
Socket for external aerlai. Complete with solid hid 
shoulder strap, earpiece and battery. 



and 



LASKY'S PRICE £5.9.6 



Post 2/6 




THE "SOKOL" 7 TRANSISTOR TWO BAND RADIO 

Super quality receiver covering the full Med. and Long wavebands with exclusive rechargeable battery 
which can bo recharged from aiiv 110/250v. A.C. mains supply. Abo operates on PPR type dry battery. 
P.M. s, oaker Ivory and black plastic cabinet 6 x 3} x liin. Socket for external nerial. Conn icte with 
real leather case, rechargeable battery and I ACI/V'C DDIPL" f*#I? A d e ° 3i 

charger, dry battery and earpiece. LMoMo llvluL 21 .£7 ,\J 2/8 



SPECIAL OFFER — MAKER'S SURPLUS 
7 TRANSISTOR PORTABLE RECEIVERS 

By famous British maker 7 transistor plus "2 diode superhet, 6 
waveband portable receiver. Operating from four 1.5 v. torch 
batteries. Cover the full Medium Waveband and Short Waveband 
31-94 M. and also 4 separate switched band-.<pread ranges, I3M. 
16M, 19M and 25M. with Band Spread Tuning. All Mullard 
Transistors and Diode Uses 4-U2 batteries. Sin. Ceramic Magnet 
PM Speaker. Ea-iy to read Dial scale. 500 MW Output. Teleacoplo 
Aerial 4 Ferrite Bod Aerials. Very attractively styled plastic 
cabinet size 10 x 6j x 3rin.. finished in mid-fawn with metal Iria 
and carrying handle. 




LASKY'S PRICE £10.19.6 



Four OS batteries 3/4 extra. 



Tel: PAD 3271 , 42 TOTTENHAM CT. RD., LONDON, W.I 



Tel: LAN 2S73 
Tel: FLE 2833 



207 EDGWARE RD, LONDON, W.2 Tel: pad jz/i ■ 4Z lOiifcNMAn ti. itu., lunuun, yy 

33 TOTTENHAM CT. RD., LONDON, W.I Tel: MUS 260S I 152/3 FLEET STREET, LONDON, E.C.4 

Both open all day Saturday. Early closing Thursday. I Both open all day Thursday. Early closing Saturday. 

Mail Orders and correspondence to 3-15 Cavell St., Tower Hamlets, London, E.I. Tel: STE 4821/2 



LASKY'S FOR SPEEDY MAIL ORDER SERVICE 



1018 



PRACTICAL WIRELESS 



April, 1966 




LAFAYETTE HA 63 

COMMUNICATION 

RECEIVER 

7 valves + Rectifier, 4 Bands 
550 Kc/s— 31 Mc/s. 'S' Meter- 
BFO-ANL-Bandspread Tuning. 
200/250V. A.C. Brand New. 
84 Clns. carr. paid. 



HA.230 DE LUXE GENERAL 
COVERAGE RECEIVER 

Wonderful value. 8 valves + rec- 
tifier. Coverage 550 kc/s.-30 Mc/s 
1 RP and 2 IF stages. "Q" multi- 
plier. B.F.O.. A.N.L.. "S" meter, 
electrical bandspread, aerial 
trimmer, etc. Brand new and 
guaranteed. £33. S.A.E. for full 
details. Also available in easy to 
assemble semi-kit form at 25 jrns. 




TEST EQUIPMENT 
Portable Oscilloscope CT.S2 

A compact <9 x 8 x 16; In.) general purpose 
scope. T/B 10c/s-40Kc/s. Bandwidth lMc/s. 
Sensitivity 40 Mv/cm. Mullard DG 7/5 
2D In. CRT. For operation on 203/250v. A.C. 
Supplied complete with metal transit 
<:aai;. strap, test leads, and visor hood. 
Brand new and guaranteed. £22-10.0. 
Carr. 10/-. 

OS 8B U OSCILLOSCOPES I 

High quality Portable American 
Oscilloscope. 31n. c-.r.t. T/B 3c/s- 
50kc/s X Amp: o-500kc/s Y Amp: 

0-2 Mc/s. Power 
requirements 

105-125v. A.C. 

Supplied in "as 




LAFAYETTE HA-SS 
AIRCRAFT RECEIVER 

108-138 Mc/s. High selectivity and 
sensitivity. Incorporates 2 RF 
stages including 6CW4 Nuvlstor. 8 
tubes for 11 tube perlormunce, 
solid state power supply, adjust- 
able squelch control, slide rule 
dial, built-in 4in.speakerand front 
panel phone lack. 220/240V. A.C. 
Supplied brand new and guaran- 
teed. £19.7.6. Carr. 10/-. 

CODAR EQUIPMENT 
.Main London Agents 

CR.70A. Communication 

Receiver £19.10.0 

P.R.30 Preselector.. £5.10.0 
A.T.5 Amateur Trans- 
mitter £16.10.0 
Postage extra. 




_ TRANSISTORISED 
:§ TWO-WAY 
^TELEPHONE 
INTERCOM 

Operative over amaz- 
ingly long distances. 
Separate call and press 
to talk buttons. 2-wire 
connection. 1000's of 
applications. Beauti- 
fully finished in ebony. 
S uppl ied complete with 
batts. & wall bracket. 
£6.10.0 pair. P.P. 3/6. 



TWO-WAY RADIOS | | 

Superbquallty.Com- . 1 L 

plete with all acces- ,- - l H ~Tl 
sories and fully g't'd. 
3T'nsistor £7.19.6 pr 
4 T'nsistor 11 gns. pr M 
9 Tnsistr £22.10.0 pr B 

> OQ trnc T\r o_ • _ 



lOTnslstr 28 pns. pr. 
Post extra (S.A.F.. 
for full details). 
These cannot be used 



._ 



in ('.A'. 



MAGNAVOX 363 Tape Decks 

New 3 speed tape deck, supersedes 

old Collaro studio deck. 

3 track. £10.10.0. 4 track. £13.10.0 



GARRARD 
AUTOCHANGERS 

nn £5. 5.0 

1000 £5.19.6 

2000 £6.19.6 

3000 £8. 8.0 

p . & p. 5/- extra. 



AMERICAN TAPE 

First grade quality American 
tapes. Brand new and guaranteed. 
Discounts for quantities. 
Sin. 225ft. L.P. 4/- 

:i!.n. 600ft. T.P. mylar 10/- 

oln. 600ft, std. plasti6 8/6 

6ln. 900ft. L.P. acetate 10/- 

5ln. 1200ft. D.P. mylar 15/- 

51n. 1800ft. T.P. mylar 35/- 

5(ln. 1200ft. L.P. acetate 12/6 
Sfln. 1800ft. D.P. mylar 22/6 

5jin. 2400ft. T.P. mylar 45/- 

71n. 1200ft. std. mylar 12/6 

71n. 1800ft. L.P. acetate 15/- 

71n. 1800ft, L.P. mylar 20/- 

In. 2400ft, D.P. mvlar 25/- 

7in. 3600ft. T.P. mylar 58/6 

Postage 2/-. Over £3 post paid. 




OPEN 9 a.m. to 6 p.m. EVERY 
DAY MONDAY— SATURDAY 
Trade Supplied. 



VOLTAGE STABILIZER 
TRANSFORMERS 

Will stabilize 
your mains 
voltage. Ideal 
lor TV receiv- 
ers and . 
trial equip- 
ment. Input 
80-120 v. unci 
160-240 v. Con- 
stant output ! 
110 v, or 240 v. 
250 watts. 
Brand new guaranteed. £10. 10.0 
Carr. 7/6. 

VARIABLE VOLTAGE 
TRANSFORMERS 

Brand New Guaranteed. Fully 
Shrouded. Input 230v. 50/60 c/s. 
Output 0-260 v. 
1 Amo £4.10.0 
2.5 Amp £5.17.6 
5 Amo £9. 0.0 
8 Amp £13.10.0 
10 Amp £17.10.0 
12 Amp £19.15.0 
20 Amp £32.10.0 
2:5 Amp Portable 
Metal Case with 
Meter, Fuses, etc. £9.17.6. 
SILICON RECTIFIERS 

200P.I.V 200mA 2/6 

1.000 P.I.V. .. 650mA 

800 P.I. V 500mA 

800 P.I.V 5 amp 

400 P.I.V 3 amp 

400 P.I.V 500mA 

150P.LV 165mA 

70 P.I.V lamp 

95 P.I.V 3 amp 

Post extra. 






Stockists of NO/V1BREX, 
SINCLAIR and all Electronic 
Equipment and Components 



ERSKINE TYPE 13 Double 
Beam OSCILLOSCOPES 

new condition. Timebase 2 c/s-750 kc/s. Separ 
fully tested. ate Yl and Y2 ampin 

£25. Carr. 10/-. to 5.5 Mc/s. calib. at 100 kc/s 
Suitable 230/ and 1 Mc/s. 110/230 v. A.C. 
115V. Transfor- Guaranteed perfect £27;10-0- 
mer. 15/6. Carr. 20/-. 



TE-20 RF SIGNAL GENERATOR 

Accurate wido range signal generator cover- 
ing 120Kc/3-260Mc/s on 6 bands. Directly 
calibrated. Variable R.F. attenuator. 
Operation 200/240 
V A.C. Brand 
new with In- 
structions. 
£12.10.0. Carr. 
7/6. 




LAFAYETTE 
NUVIST0R 

GRID 
DIP METER 



Compact true ono 
hand operation, 
iquency ran 



LAFAYETTE 46 

RESISTANCE CAPACITY 

ANALYSER 

2pF. 2.000 mFd, 2 ohms. 200 1.7-180Me/s. 230v. 
megohms. Also, checks impe- AC operation, 
dance. Turns ratio. Insulation Suppliedcomplete 
2O0-250v. A.C. Brand New. £15. ' with all coils and 




carr. 7/6. 



instructions. £12.10.0. carr. 5/-. 




CLEAR PLASTIC PANEL METERS 

First grade quality. Moving Coll panel meters 
available ex-stock. S.A.E. for illustrated 
leaflet. Discounts lor quantity. Availabl 
follows. Type MR38P I 21/32in. square fronts. 



2mA .. .. 22/6 

omA .. .. 22/6 

10mA .. .. 22/6 

20mA .. .. 22/6 



s METER 

BOLtA 
J 00:j. A 
200!iA 

r.(K)'j.A 

50-0- 50 (1A.. 

HW-0-lOOu.A 

BOO o-aoonA 

1mA 

POST 



29 6 
32/6 

:;;>/6 

27/6 
25/- 
29/6 
27/6 
22/6 
22/6 
EXTRA 



50mA . . 
100mA . . 
150mA .. 
200mA .. 
300mA .. 
500mA .. 
750mA .. 
1-0-lmA 
IA. DC .. 
2A. DC . . 
5A. DC . . 



22/6 
22/6 
22/6 
22/6 
22/6 
22/6 
22/6 
22/6 
22/6 
22/6 
22/6 



3V. DC . . 
10V. DC 
20V. DC 
50V. DC 
100V. DC 
150V. DC 
300V. DC 
500V. DC 
750V. DC 
15V. AC 
50V. AC 
160V. AC 
300V. AC 
500V. AC 



22/6 
22/6 

22 ,6 
22/6 
22,6 

me 

22/U 
22/6 
22/6 
22.6 
22/6 
22/6 
22/6 
22/6 



"S" Meter lrnA 29/6 



Larger sizes available— send tor lists. 




TE-51 NEW 

:!0,000a VOLT 
Ml I.TI- 

METEft 

0/6/60/120/1,200 
V. A.C. 0/3/30/60/ 
300/60C/3.000 v. 
D.C. 0/60uA/12/ 
300 IDA DC. 0/ 
60K/6 Meg. ohm. 
£4.5.0. Post & 
packing. 2/6. 



m 

5/6 
7/6 

7'6 

m 

ii- 

3/6 
5/6 



MODEL PV-5S VALVE 
VOLTMETER 

] I llirK. Input. 

DO Mil runm-. I. 
1.800 v. 7 AC v< 
raagM l.r,-i.:,iiri 
4,000 Peak Ui Peak 

K.-.i-t ,h, . .2 .l.ill !., 

1 ,000 megohm. Deoi- 

i»i» —10.111 to 

fISdB. SuppllL-.l 

bruid new »iih In- 
itmcl Ion* lea.I- un<l 

J12.10.0 P. 4 P. 3/0. 



TS-76 20.000 O.I'.V. Push lluiion 
iMuHI-Tester 

|Simple operat'n, 
D.C. volts up to 
l.OOOv. A.C. volts 
up to 1.000 v. 
Resistance up to 
10 megohm. Cur- 
rent up to 250mA. 
Decibels — 20 to 
+36dB. £5.5.0. 
P. & P. 2/- 






MODEL 500 
30.000 o.p.v. 0/.5/ 
1/2.5/10/25/50/100/ 
250/ 500 /l.OOOv. 
DC 0/2.5/10/25/ 
100/250/500/1.000 
V. AC 0/50-J.A/5/ 
50/500mA/ 12amp 
DC. 0/60K/6 

Meg/60 MegQ. 
£8.17.6. Post 
Paid S.A.E. for 
full details. 




% (RADIO) LIMITED 

Pnone: GERHARD 8204/9155 
Cai/es. SMITHEX LESQUARE 

■34 LISLE STREET, LONDON , W.C.2 



April, 1966 



PRACTICAL WIRELESS 



1019 



SURBITON PARK RADIO 



pFAf»mi3l AUDIOKITS &REC0RDAK1TS 

F.M. TUNER UNITS Nos. 15, 16 and 17 Cash £12-17.6 

Or Dep. 51/6 and 12 m. pymts. 0/18/10 (H.P. Price £13.17.6) 

TRANSISTORISED AMPLIFIER with 5 position input selector, 
pre-atnp and controls, 10 watt amplifier and Power Pack 

For 3 Ohm Speaker Cash £14.5.0 

Or Dep. 57/- and 12 m. pymts. 20/10 (.H.P. Price £15.7.0) 

For 15 Ohm Speaker Cash £15-8.0 

Or Dep. 62/- and 12 m. pymts. 22/6 (H.P. Price £16.12,0) 

All above include Front Panels, Knobs and Instruction*. 
TWO TRACK RECORDAKIT AMP. (Valve) FOR STLDIO 

DECK. 6 valves, controls, self powered Cash £11.11.0 

Or Den. ill- and 8 m. pymts. 25/6 (H.P. Price £12.11.0) 

FOUR TRACK AMP. as above Cash £12.120 

Or Dep. 52/- and 8 m. pymts. 27/6 (H.P. Price £13.12.0) 

Case for either of above tape amplifiers and Studio deck £5-5-0 
TAPE PRE-AMP for Studio Deck, self powered. 

Two Track.... Cash £8.8.0 

Or Dep. 34/- and 6 m. pymts. 25/8 (H.P. Price £9.9.0) 

TAPE PRE-AMP as above Four Track — Cash £9.9.0 

Or Dep. 39/- and 6 m. pymts. 28/4 (H.P. Price £10.9.0) 

All the above amplifiers are for the STUDIO deck which Is no 
longer available. The Martin Recordakits will be modified for 
the new Macnavox deck in due course. Details will be forwar- 
ded to enquirers when to hand. 
We are leading stockists for all Martin Constructional Kits. 

UifiMJIUN: *.-nin*Ma.i Selection 

ARMSTRONG 281 10-10 watts Stereo, Magr PU and Filter 

Cash £33.15.0 

Or Den. 135/- and 8 m. pymts. 49/6 (H.P. Price £36.9.0) 

ARMSTRONG 828 10-10 watts Stereo Amplifier Cash £27-10-0 

Or Dep. 110/- and 12 m. nymts. 40/4 (H.P. Price £29.14.0) 

ARMSTRONG ISA F.M. Tuner Powered Cash £22.10.0 

Or Den. 90/- and 12 in. pymts. 33/- (H.P. Price £24.6.0) 

ARMSTRONG 883 AM/FM TUNER Powered Cash £28.15-0 

Or Dep. 115/- and 12 m. pymts. 42/2 (H.P. Price £31.1.0) 

ARMSTRONG 127 MONO 5\V with AM/FM Cash £26-100 

Or Dep. 106/- and 12 m. pymts. 38/10 (H.P. Price £28.12.0) 



SURBITON PARK RADIO LTD. 



ARMSTRONG 187 STEREO as above Stereo amp Cash £37.10.0 

Or Dep. 150/- and 12 m. pymts. 55/- (H.P. Price £40.10.0 

ARMSTRONG Stt MONO 10W amp. with AM/FM Cash £36-15-0 

Or Dep. 147/- and 12 m. pymts. 58/10 (H.P. Price £39.13.0) 

ARMSTRONG 837 STEREO as above with Stereo Amp. 

Cash £52.15-0 

Or Dep. 211/- and 12 m. pymts. 77/4 (H.P. Price £56.19.0) 

ARMSTRONG 226 STEREO as above, but Mag;. P.U. Filter. 

Cash £61.0.0 

Or Dep. 260/- and 12 m. pymts. 88/- (H.P. Price £65.16.0) 

Teak Cases for all Armstrong: Units £3-10.0 

ROGERS CADET Mk. 3 10-10 watt Stereo Amp. Mag-. P.U. 

Cash £29.10.0 

Or Dep. 118/- and 12 m. pymts. 43/3 (H.P. Price £31.17.0) 

CASE MODEL ROGERS CADET Mk. 3 £3.0.0 extra 

LEAK STI'.RKO :J0 TRANSISTOR AMPLIFIER. .Ca?h £49-10.0 
Or Dep. 198/- and 12 m. pymts. 72/7 (H.P. Price £53.9.1) 

IWHtHJIJMJiU Selection 

FANE 128/10 Heavy Duty 12tn. 20 watt Cash £5.17.6 

VIIIAKI II). \l K SUPER g/RS/DD Cash £7.0.0 

\VH ARFEDALE SUPER 10/RS/DD Cash £11-13-4 

Or Dep. 47/6 and 8 m. pymts. 25/9 (H.P. Price £12.13.6) 

GOODMANS MAXIM Cash £17.10.6 

Or Dep. 70/6 and 12 m. pymts. 25/8 (H.P. Price £18.18.9) 

FiWlMifBaMaUja Selection 

GARRARD SRPI0 Mono Cash £5.10.0 

GARRARD Model 1000 Mono Cash£7.10.0 

Or Dep. 34/- and 6 m. pymts. 26/- (H.P. Price £9.10.0) 

G ARRARD Model 3000 Stereo Lightweight arm Cash £11.11.0 

Or Dep. 47/- and 8 m. pumts. 25/6 (H.P. Price £12.11.0) 

GARRARD S.P.25 Less cart.: Single player Cash £12-10.0 

O' Dep. 50/- and 8 m. pymts. 27/6 (H.P. Price £13.10.0) 

GARRARD AT60 Less cart.: Heavy table Cash £13.0.0 

Or Dep. 52/- and 12 m. pymts. 19/- (H.P. Price £14.0.0) 

GARRARD la It so Push button oper.. less cart Cash £27.10.0 

Or Dep. 1 10/- and 12 m. pymts. 40/4 (H.P. Price £29.14.0) 

GARRARD 401 Transcription Table. No arm Cash £32.10.0 

Or Dep. 130/- and 12 m. pymts. 47/8 (H.P. Price £35.2.0) 

COLORING G66 Mono Single Player Cash £11.11.0 

Or Dep. 47/- and 8 m. pymts. 25/6 (H.P. Price £12.11.0) 

COLOR ING GL6S Less cart. Pickup lift Cash £19.10.6 

Or Dep. 78/6 and 12 m. pymts. 28/7 (H.P. Price £21.1.6 

COLORING GL70 Less cart. PU lift. Heavy table Cash £29.18-6 

Or Dep. 120/6 and 12 m. pymts. 43/9 \(H.P. Price £32.5.6) 

TERMS: C.W.O. or C.O.D. ALL ITEMS CARRIAGE FREE 

Leaflets available upon receipt of fd. stamp 

48-50, Surbiton Road, Kingston-on-Thames, Surrey 

Phone KIN. 5549 :: Hours 9 a.m. to 6 p.m. daily (I p.m. Weds.) 



elf 



£j? 



*i\cs. 



t*M, 




f« 






» 



The New'Picture-Book'wayof learning 



3ACIC ELECTRIC1TY(5vols) 
DA3IW ELECTRON ICS(6vols) 



#«*• 



-*• 






*#: 



You'll find it easy to learn with this out- 
standingly successful new pictorial method — 
the essential facts are explained in the 
simplest language, one at a time; and each 
is illustrated by an accurate cartoon-type 
drawing. 



The books are based on the latest research 
into simplified learning techniques. This 
has proved that the Pictorial Approach 
to learning is the quickest and soundest 
way of gaining mastery over these 
subjects. 



The series will be 
of exceptional 
value In training 
mechanics ana 
technicians in electri- 
city, Radio and Electronics. 

WHAT THIS MONTH'S 
ENTHUSIASTIC READERS SAY 

EVERY DAY WE RECEIVE LETTERS PRAISING THESE 
BOOKS, HERE ARE A FEW FROM THIS MONTH'S POSTBAO. 

" , . . 1 cannot tell you how delighted I am with them ..." 

G.N., B.F.P.O. 64. 
" . . . / have been supplied with BASIC ELECTRICITY 
and BASIC ELECTRONICS, and needless to say I am 
delighted with them, and wish to congratulate you for pub- 
lishing one of the best ever series dealing with this complex 
subject . . ." P.B., Worthing. 



POST A/OW FOR THIS OPFBRf! 



To Selray Book Co. 
60 Hayes Hill, Hayes Bromley, Kent 

Please send me Without Obligation to Purchase, Basic Electricity/ 
Basic Electronics on 7 Days Free Trial. 1 will either return set, 
carriage paid, in good condition within 8 days or send down payment 
of 15/- (Basic Electricity) followed by 6 fortnightly payments of 
10/-. Down payment of 15/- (Basic Electronics) followed by 
6 fortnightly payments of 12/6. Alternatively, 1 will send 68/" 
(Basic Electricity — 5 parts), 81/- (Basic Electronics — 6 parts) post 
free. This offer applies to United Kingdom only. 
Tick against set required {only one set allowed on free trial). 

BASIC ELECTRICITY D BASIC ELECTRONICS □ 

Signature 

(// under 21, signature of parent or guardian) 

| NAME 

i ' BLOCK LETTERS BELOW 

T 

J? FULL POSTAL 

.ADDRESS 



1020 



PRACTICAL WIRELESS 



April, 1966 




mmiMMMMm 



HI-FI AND TAPE EQUIPMENT 



RADIO 



KITS 



ELECTRONIC COMPONENTS 



i Designs by MULLARD- 
Interpreted by STERN 



Justly famous— superb Hi- 
Fi designs from the Mullard 
Applications Research 

Laboratory, meticulously 
executed by Stern and 
Veritone. Buy them as 
hand-built and tested 
units, or in Stern-Clyne'i 
famous Homebuild Kit 
lonn. Either way provides 

performance per £ unequalled anywhere. II you ore working to a budget, kits offer a real saving plat real building 
ntlflaction. Each is absolutely complete and backed by comprehensive. eaJy-to-lollow building instructions. 




FIVE-TEN AMPLIFIER 

One ol tbe most famous amplifiers ever made— thousands are In service as 
the nucleus of high quality installations throughout the world. Check Ihu 
phenomenal performance, unmatched bv anv other amplifier obtainable 
in thi« price range: Frcq. response fl o/.i. to :U) ko's. flat 1 .lb. OI«tortion 
ull 10 watts output. Noine — 05 do. below 10 wans. Input signal 
40 rnV. for 10 watts. Out. Imp. 3 or 18 ohm«. Valves Bf81, KF»>:. BCC8S, 
:. s;?e overall: in x 7 x Mag. Ugh. Im.TiM.rate- main- OVUM to* 
gram and aox. supply of 8S0 v. at 45 mA. and 9.8 v. at •_',' amp«. for pre-arnp. 
tnner. etc. To full Milliard specification. Assembled and tested £13.10.0 
Kit £10. ftm.iiO. FIVE-TEN AMPLIFIER AND TWO-VALVE PRE-AMP. 
Assembled and tested £21.10.0. Kit 15 gns. lid i II rarriaar. FIVE-TEN 
AMPLIFIER AND THHEE-VALVE PRE-AMPL1FIER. Assembled and 
tested £85.10.0. Kit £19.10.0. AM " 8 nrrrtas* 



NEW 



PORTABLE 
TAPE RECORDER 




SUPERB NEW STERN-CLYNE FMI 




Exceptionally low-priced, but 
actually a robustly made 
reliable instrument which can 
be used anywhere lor note 
taking, idea recording, dicta- 
tion, etc Me. ham 
I. .Hit -.ii lo ri|(i.l BtMl oha»M» 
■ad hOBtCd In lough grey 
..:.. -ii ...-.• arNb .currying 
OH .ii.i i •..•in plastic tape 

... rin.-.i with 
abuse anual-teleokif fund Ion 

Hand microphone has stop' 
start llinmbswilcli for re- 
mote .-..Html of I 

piiiybn.k ban 

Complete with tape and 
span spool, ndka mnl mluln- 

,■.,,.,■. Hi/.' i.uly: 
in. high. £6.19.6. 
Carriage I . 

V.H.F. TUNER 



Specially designed 
ar the Amateur 

utltler. a new len- 
itive tuner unit that 
rovlde 



iter 



e-Ii 



BBC FM 
ilssions. High 
quality-output -lunal 
DPtiminii 
perfonuaueo from 
any Hi-Fi uu.ll.i 
ufierb styl- 
ing make- for har- 

i bos In-tull- 

iiil.in with existing 
equipment. Reliable 

•tkdj aligned clr- 
cult employ-- 111' 
stage, tune.l-ano.le twncil-irri.l freq. changer. 2 IFV, nol-- Iltnlter ami 
ratio deteolor. Valves an: 4 x Ei'M plu« 2 diode.-. Input soda, imimV 
for 40ilR. HM. Wp* than 1°„ Ii lull 'levlntloii. Power reqd. 200v. at 
SOniA and 6.3v. at 1.8A. Panel black anil sUver-grey, size Bxflm.1 
cadmium plated, nverull depth 4)in. FMI Kit of parts with Instruction 
Handbook. £7.9.6. rarriaar 41-. FMI Assembled and tested. £10.9.6. 
Carriage 4/-. Optional Power Pack Typo D. Kit ol parts. £2.15.0. Oaniaft 
3/6. Power Paok Type D. Assembled and tested. £3.10.0. (torrid 
Handbook only, 8/- post free. Descriptive leaflet on KCJOMt, 



TWO-VALVE PRE- 
AMPLIFIER 

Specially designed for 0M with the 

Milliard <erie» of 3. 10 and 20 watt 

• i.i I- I. -.nimble far all 

Hit. power unit- not requiring input of 

mora Una 880 nV for iuii output. 

Feature include input' for crystal and 
variable reluctance pirk-ups with RIAA 
equalisation, plu* radii), sensitive 
ml. r..|ihone, and tape replay direct or 
from pit limp, i .iitrola include 6- 
se lector, volume and wide 
in.;, i.i . and treble boost. Valves 
9 x KFS6. -I*.- 1)| x 4! x 2» in. 
high. Panel 10} x 2J In. Requires 
300 v. at :i mA. and 6.3 v. at O.ti anrps. 
Assembled and tested £9.10.0. Kit £8.8.0. 
Add CI- rarriaar. 




THREE-VALVE PRE- 
AMPLIFIER 

rspeclallv recommended for u«o with the 
ft-lo ampin ,i. inn i.i-,, mJUble far oat 
with nil MoUard sates mono HsnOBan 

mi.l any high quality unit requiiiia .in 
u| to WO "i\. for full output. 
.. lode: a. Ida rani B 
Treble control", high and low po>« 
lliters, auxiliary Input and record out- 
put sock.l-, twitched input-. SO! CJJUHj 
or magnetic pick-ups, radio, tape play- 
back Ms] in t IHtl r Power required 
2f>() v. at 6 mA, and 6.3 v. at 1 a:np. 
Valves U x EK8rt and ECCS3. Slse 
11 x 41 x 4ln. high. Panel 12 x 4jln. 
Assembled and tested £13.13.0. Kit 
£10.10.0. Aid 61- rarrlagt. 



TEST 7 

Pocket 

Multimeter 

39/6 



A really versatile instrument that makes 

a handy, pocket size tool, M nun - \. 
. ir IX' vol laid ii I lire, range- of 0-1S-1 80- 
1000 v. Rclktance 0-11)0,000 ohms, and 

Current 0-lflO mA. D.O. Btae only: 

SJ | 3i x ijln., with ingenious dial 
design, providing a clear, .-a-ilv r.-a.t 
wale. Complete with battery and test 




MAGNAVOX 363 
TAPE TRANSPORTER 




Manufactured to precise limits that 
permit recording and tape playback 
to the highest standards set by the 
Music Industry. simple reliable 
employs a swale high-duty 

i> Ith heavy fly wheel. Features 
include fast wind on arid rupl.l . ■ 
paase control, 3-speed selection with 
fetterlock, bfdtvin r.-volutton indi« 
color, piano key controls. Hpeede 1». 

i 7| l.pA Wow and rliitlrr 
0.16% on 7} l.p J . M ax. epool »i/. , in. 
Playing time up to 120 mln. per track 
from 1.200ft. standard tape. Mm 
13) x llin. plus Sjin. below mounting 
board. With i track beads. £10.10.0. 
With 1 track beads. £3.19.6 Add 
10/- carriage and 



HF/TR3 TAPE AMPLIFIER 



Easily tbe best complete tape amplifier 
available to the home builder. Supplied 
already matched for tbe Masnavot 363 
tapedeek. 

Features Include: switched equaliz- 
ation for all speeds (O&R 
Hlandardi at 7J i.p.i.) Trehle boost 
ii... i t-orated daring Record. Ba^ 
boost during playback. speaker 
output inatehed for :<.7.i. uud 19 ohiu% 
u.tdllloiial output. lot exit 
speaker, phOfM mi ■ nit., r log On BOOOsd 
and Hi-Fi playback through existing 
i, tnpui- for Mic. Pick-up. and 
\ III' Radio. Valve*: Kl'sii. i 
IA-4. BM81, BISSl, Hi/..- overall: 
11 x fi x ilin. (Panel 181 x I In. , 
Power pack on separate cha*xi* SsM 
7i x 3 x 4Jin. Amp. & power pack 
Kit ol parts £13.135. Assembled and 
tested £18. Add 7/6 carrloae. 



TAPE PRE-AMP TYPE 'C 




Specially developed by Mullard 
Laboratories tor use with high quality 
replay systems, and supplied specifi- 
cally matched lor use with tbe 
Magnlvox 363 tapedeek. Feature,* 
include: ferroxcube pot core inductors 
for treble equalisation, push pull 
or incorporating fertxixoo.be 
transformer, adjustable oulpui (or 
matching to existing high-quality 
atiiplilU-r system.?, inputs for Mic 
Pick-up, Radio, etc. Valves: 8 x. 
HF86. B08S and BM8L Totally 
enclosed in case size Hi x 6J x :iiln. 
blgb. (Panel 11} x 3J In.) Power 
supply of 300 vdo at 2fi mA. and 
6.3 v. at l.li A, ;.. on separate sub- 
cluusbl slse 01 i 41 i 4Sln. high to 
facllltafe remote location trot 
beada, Pre-amp and power paok Kit 
ol parts £14. Assembled and tested 
£19. 10s. Add 7/0 carriaat. 



April, 1966 



PRACTICAL WIRELESS 



1021 



CLEAR-OUT OFFERS OF WELL-KNOWN HIGH GRADE EQUIPMENT 

PRICES SLASHED TO MAKE WAY FOR NEW STOCK RANGES! 

Genuine Bargains! Original prices quoted are exactly those at which we have sold previously. 




FAMOUS MULTI-TESTER 

AT TWO-THIRDS USUAL PRICE! 

•Type 200H— 20 ranges, 20,000 obmi per voll sensitivity. 
Blue only 31" z 41* x 1" deep with Ingenious dcslgu 
provldlng an extra large, easily read aosle. 
Magnificently damped Jewelled ui-ter move- 
ment. Fitted with low low, long life ceramic 
selector switch, complete with leads and teat 
prods, battery and full instructions. 
Ranges: DCtri ii-5-25-.Vi.250-2500. ACv: 0-10-jO- 
100-600-1000. DO Camnt: 0-50 [iA, 0-3.8, 230mA. 
Resistance 0-6K-6M. Cap: 10u.F-0.001 uJF and 
0.001 iiF-0.1|xF. Output: —30 to +22dB. 

WAS NOW1 SAVE 

£5.5.0 £3.10.0 £1.15.0 

•Add 2/6 p. db p. 

DUVIDAL CROSSOVER NETWORKS 

Superb construction us- 
ing selected high-grade 
components, each hand- 
somely finished and con- 
st runted in metal case 
with Integral mounting 
feet. Inputs and speaker oulpu' - 
are made to standard screw 
terminal?. Full Instructions 

■applied. 

CV-1 Variable Crossover— Hlan- 
dard 2- way unit (or use with 
low to medium power woofer 
and tweeter arrangement. Vari- 
able control permits adjustment of ban and treble output levels. In bronze Wnt-fci^ 
case with black plastic panel size 4 X 2j s l|io. high. 

WAS £1.2.6 NOW I2'6 SAVE 10'- a/ -p .a f.mtO*n. 

CH-2 Crossover He*work— HI-FI 2-way iron-cored choke and filler system offering 
high frequency crossover at 2600 or 3600 cycles/sec. Totally enclosed in bronze 
llnhhcd taut site 3} i 8J i Hit,, high. 

WAS £2.9.6 NOW 25'- SAVE £1.4.6 a/- p. * p. and c<---. 

HN-3 Variable Crosaover— 3-way, medium and high power variable level unit offering 
nild-range crossover at 800 c/a and tweeter crosaover at 3300 c/a, together with "L'" 
Pad variable level controls for mld-ransc and tweeter outputs. Matching arrange- 
ments also permit- u*e as 3-way crossover, or without level controls when speaker, 
efficiencies are equal. Handsomely finished In 2-tone grey metal case size 6 x 3 x 2ln- 
nlgh. 

WAS £4. 1 0.0 N O W 50'- SAVE £2 s/e p. a p. ,*■ can. 
WESTWELL CT-2B TWEETER 

Adds sparkle and realism to the performance of almost any high 
quality reproducer. Nominal 2j dlam. moving coil unit Is 
attached to translucent bronze flange with matt black grille for 
mounting In or oul-i.lo cabinet ; alternatively detachable bracket 
can be used. Impedance 10 ohms. Hating 10 w max. 6 w nom. 
Recommended crossover frequency 3000 c/s. Sensitivity 103 
dB/W. Size overall: 3 x 3 x ljln. deep. 




WAS 27/6 NOW I9'6 SAVE 8'- 



3/- P. & P. and 



New American branded tape by world renowned manufacturers, and equal In quality to 

fbi beet obtainable anywhere, liusrantced splice free, red oxide coaled, with full 

ponse and uniform output. Resistant to moisture, heat, cold and 

n. Available in a wide range of Acetate and Polyester qualifier, each di-tim.- 

i-'Xed and cellophane wrapped In colour coded cartons ahowiug recording 

times at 7J, 3; and li l.pj. Compare the prices! 



Ranee available 
Polyester 
:;;m. tiflOft. Double Play 11/6 
7in. 1.300ft. standard 12/6 
Ban. 1.900ft. Double Plav 15/- 
"in. 1.800ft. Long Play 20/- 
6Jln. 1,800ft. Double Plav 22/6 
Tin. 2.400ft. Doubio Plav 25/- 



Aoelsle 
ftlu. 000(1, Standard 8/6 
6m. 900ft. Long Play 10/- 
Djln. 1.200ft. Long Play 12/6 
Both type* poof a*M | 
i I- pur reel. Pour or more 
reels poll iter. 



BULK TAPE ERASERS 





There are actually miniaturized, high quality version* of the powerful 
demagnetizes used in Instrument and aircraft manufacture, and 
represent the most effective way of restoring recorded or noisy tape 
to Its original unmarked condition. Essential when using high fidelity 
recorders in conjunction with high-grade tape: pays for itself over and 
over in preserving expensive tape performance. Bulk oraaen an also 
bo used to demagnetize small parts and tools, and for demonstration 
purposes, etc Recommended types available: 

Model HT-120 

Cleans up to "In. reels of tape In seconds. For 380/250 v A.C operation. 

Size: 4{ x 4 x 2Jln. nigh. Finished grcv crackle. 

WAS £5.5.0 NOW 67'6 SAVE £1.17.6 

4/- P. HP. and Can. 
Hodel 176 

Extra powerful professional model. Cleans tape reels m all sizes np 
to inin. dinm. Size 71 x 4} x 3Jln. high. Finished grey crackle. 

WAS £7.7.0 NOW £5 SAVE £2.7.0 

r. £•/'. and Can. 

DUVIDAL SM-5 TRANSISTOR- 
ISED MONO/STEREO MIXER 

Compact, rel (-contain- 
ed 4-channel audio 
mixer providing 4 scp- 
parate. Infinitely vari- 
able input! mi mono or 
twin input.-, for left and 
right channels on 
-leixo. Superbly oon- 

. and handsomely styled, ind 
finished In bronze enamelled case size 
6 x 3 x Sin. high. Internal PP3 battery 
gives approximately 400 hours operation. Input suitable for xtal, 
loudspeaker used as mike, low Inp. mike with trans, radio, tape, etc 
Max. input 1.6 v. max. output 2.5 v. gain 6 dB. Inputs through 
standard Jack plug socket; outputs through phono plugs. 

WAS £3.17.6 NOW £2.15.0 SAVE £1.2.6 

3/6 P. A P. and Can. 




VERITONE NEW, ADVANCED COMPACT 
COMMUNICATIONS RECEIVER 



HHiHiitiiiiHiJii.iimnjiiiim.iJi 




IKE 



ELECTRONIC CENTRES... 
most exciting shops in Britain/ 



New. highly developed, extremely compact design. Veritone SR.1S0 
bit portable radio proportion! and a DX perlormance comparable with 
many highly expensive, professional receivers. Frequency mverage Is 
continuous from 040 Kc.'» I I bands, pita bandrpread on 

Ham frequencies of U, 7, 14, ami US Me.-. Features Include: extra 
large, el.aily marked dial. •.-" mcaar, Ullrtlll "||H|<| BFO. noise 
llmller, built-in loudspeaker and cxtenda as to receive 

all but m—l distant stations. Extras Include phone outpui Jack, 
standby switch, etc Size only: 13! » 8 * sin. deep. Valves I2BK6, 
13AV6. 12BA6 and S0C8 plus silicon rect. Invaluable for DXcr's. 
marine band listeners, etc. Housed In handsomely 
flnlahed metal ease. For 200/360 volts AC or DC 
Supplied with V2S-paoe "Wlnleu World Uuide lo 
Mroudcatlinii Stalioiu." 



Member of the Pantiya Group of Companies 

MAIL ORDER & ALL ENQUIRIES TO: DEPT. PW, 3-5 EDEN GROVE. HOLLO WAY, LONDON, N.7. Tel. NORtn 8161/6 



LONDON. 

18 Tottenham Court Road, W.l. 

23 Tottenham Court Road, W.L 

309 Edgworo Road, W.2. 

in;: Kl-et <m t, K.C.4. 

162 Hnlloway Road, Bf.7. 

S Cambcrwell Church Street, 8.K.S 

220 Ed snare Road, W.2. 



MTJS 6989/0095 

MDSeura 3451 

PADillnBton 8963 

FLEet Street 5812/3 

NORth 7941 

RODney 8875 

PADdinstou 5607 



CROYDON: 12 Suffolk House, George St. MUNielpal 3850 

BRISTOL: 28 Merchant Street. Bristol 1. Tel. 20861 

LIVERPOOL: 52 Lord Street Royal 7460 

MANCHESTER: 

2d 23 Withy Grove. M/c 4. Blsoklriars 6379'5248 

SHEFPIELD: 126 The Moor Sheffield 29993 

NOTTINGHAM: Eaetown Honsc. Lincoln SU Tel. 45889 



HIRE PURCHASE? 
CERTAINLY! 

Easy payment terms available 
on all kits and assembled 
equipment value 810 or more. 
Let us have your enquiry. 






1022 



PRACTICAL WIRELESS 



April, 1966 



26ign TAPE RECORDER 
for ONLY £19.10. ^^^ 

carr. 12/6 

Bargain of the Year Offer 
— cancelled Export Contract 

Famous manufacturers brand new 
unused and factory tested 2 speed, 
32 and 7 J i.p.a. twin track tape 
recorder 3 Watt output. Tape 
position Rcv.-counter, fast for- ^ 

ward and rewind, take 7* reels, 
mike and gram input. Straight 
through amplifier facilities. Out- 
pat socks'* for ext. speaker, 
monitor or external amplifier. 
Super-Imposed switching magic 
eye recording level and mains neon Indi- 
cator. Volume and tono controls 7' r 4" 
speaker. Attractively styled cabinet 

w.th detachable lid mike and reel storage facilities. A.C. 200/250 volts 
operation- Complete with crystal mike, tape spare reel and screi 




l lead 



RECORDING TAPE— Reduced Prices 

Famous American Columbia (CBS) Premier Quality Tape at REDUCED PRICES. 
A genuine recommended Quality Tape — TRY III Brand new. boxed and fully 
guaranteed. Fitted with leader and stop foils. 

Standard Long Play Double Play 

Bin. 600ft. 18/- 800ft. 17/6 1, 200ft. 31/6 

BJln. 900ft. 16/- 1,200ft. 19/6 1,800ft. 37/6 

7in- 1,200ft. 21/- 1,800ft. 28/6 2,400ft. 47/8 

P. & P. per reel 1/-. 6d. on each additional reel. 
SPECIAL BARGAIN. 3in. Message Tape, 150!t„ 3/9. P. « P. 6d. Sin. L.P. 2251L. 
4/9., 3in- D.P. 30 II., 6/8. ,., „, „ „.. 

Plastic Tape Reels 3ln., 1/3; 5in., 2/-i 5{m.. 2/-; 7in.. 2 3 

Plastic Spool Containers Sin- 1/9; 5}in- 2/-: .in., 8/8 



Alumin. Chassis. 18g. Plain Undrillcd, 
folded 4 sides, 2* deep. 6" x 4", 4/6; 
8' z 6% 6/9; 10* x 7*. 6/8; 12* x 6*. 
7/6; 12" x 8*. 8/-, etc 
Alnmin. Sheet. 18g. 6* x 6*, 1/-; 
6* x 9*, 1/6; 6* x 12*. 12/-; 12* x 12*, 
4/6, etc 



Jaok Plugs. Standard 2J* Igranic 
Type. 8/6. Screened Ditto. 3/3. 
Miniature ser. li", 2/3. 3ub-min. 1/3. 
Soldering Irons. Mains 22/220V or 
230 269V. Solon 25W Inst., 24/8. 
Spare Elements, 5/6. Bits, 1/3. 
65w*. 29/6. etc 



6 VALVE AM-FM TUNER UNIT 

Med. and THF 190m-550in, 86 
Mc/s-103 Mc/s. 6 valves and metal 
rectifier. Self-contained power unit. 
A.C. 200/250V operation. Magic-eye 
indicator, 3 push-button controls, 
on/ofl. Med., VHT. Diodes and high 
output Sockets with gain coutrul. 
Illuminated 2-colour perspox dial 
11 j- x 4", chassis size lli" x 4" x BJ". 
A recommended Fidelity Unit for use with Mullard "3-3" or "6-10" Ampll- 
flora. Now available as complete kit as illustrated, inc. • 

power unit. Carriage 7/0. /Ill I A 

Ditto, but less power unit, £9.19.6, carriage 7/6. SIWil/iW 

Circuit and construction details. 4/6, free with kit. Carriage 7/6. 




Condensers — Silver Mica, All values 
2pF to l.OOOpF. Bd. each. Ditto 
Ceramics 9d. Tub. 480V T.O.C. etc. 
0.001 mFd to 0.01 and 0.1 '350V., 
9d. 0.02-0.1/aOOV., 1/-. 0.25 Hunts 
1/6, 0.5 T.C.C. 1/9, etc.. etc. Close 
Tol. S/Micas— 10% 5pF-500pK 8d. 
6O0-5,0OOpF, 1/-. 1% 2pF-100pF. 
9d. lOOpF-SOOpF lid. 575pF. 
S.OOOpF. 1/6. Resistors— Full 
Range 10 ohms-10 meg. ohms 20% 
i and JW, 3d.. JW. 5d. (Midget 
tvpe modern rating) 1W. Si, 2W, 
W. Hi-8Ub. 5% jW, 8d. (100 
ohms-1 meg). Other values Bd. 
1% » w . 1/8 etc. eto. 



JASON FM TONER UNITS. 
Designer-approved kit of parts. 
FMT1, 5 gns. 4 valves, 20/-. 
FMT2. £7.10.0. 5 valve. 35/-. JTV 
MERCURY 10 gns. 3 valves 28/6. 
JTV2 £13.19.6. 4 valves. 28/6. 
NEW JASON FM HANDBOOK. 2/6. 
48 hr. Alignment Service, 7/6. 
P. 4 P. 2.'6. 



Volume Controls — 5 K-2 Meg. ohms. 
3in. Spindles. Morganitc Midget 
Type l»in. diam. Ouar. 1 year. 
LOG or LIN. ratios less 8w. 3/-. 
DP. Sw. 4/8. Twin 8tereo less 8w 
7/6 100k to 2M ohms with DP Sw. 
9/8. 

WAVECHANQE SWITCHES. 1 p. 
12-way 2p. 2-way, 2 p. 6-way. 
3 p. 4-way. 4 p. 2-Vay, 4 p. 3-way, 
long spindle, 3/6 ea. 



MULLARD "3-3" & "5-10" 
HI-FI AMPLIFIERS 
3 ohm & 15 ohm output 

"3-3" Amp. 3 valve, 3 watt ht-fi 
quality at reasonable cost. Baas Boost 
and treble controls quality soctional 
output transformer, 40 c/s-25 kc/s 
+ 1 dB, lOOmV for 3W. less than 1% 
distortion. Bronze escutcheon panel. 
Complete Kit only 7 gns. Carr. 7/6. 
Wired and tested £8.10.0. 

MULLARD "5-10" AMPLIFIER. B valves 10W 3 
and 15 ohms output. Mullard's famous circuit with 
heavy duty ultra-linear quality output transformer 

Basic amplifier kit price {Q I Q A Carr. and Ins. 7/6. 

Ready built 11{ gns. fc#. • #»»» 

CONTROL PANEL KIT. Bass, Treble and Volume controls with 4-posltion 

selector switch for radio tape and 11 in. x 4in. escutcheon panel. 

AMPLIFIER KIT AND CONTROL PANEL KIT. £11.19.8. Ditto, really wired 

2-VALVE PRE-AMP UNIT. Based on Mullard's famous 2-v»lve (2xEF86) 
circuit with full equalisation, with volume, bass, treble and 5-posltion selector 
switch. 8lze 9 x fi x 2 t in. Keadv Buill £7.19.6, Carriage 3/6. ^^ 




DE-LUXE 
RECORD 
PLAYER 
KIT 




Incorporating 
4 8p. Garrard 

Auto-Slim unit andMullardlatest 3 watt 
printed circuit amplifier (ECL 86 and 
fez 80), vol, bass and treble controls, 
with 8" x 5" 10,000 line speaker. 
Contemporary styled 2-tonc cabinet, 
charcoal-grey and off-white with 
matching blue-relief. Size 17J" x 16' x 
8*. A stylish unit capable of quality 
reproduction. Circuit and const, details 
2/6 (free with kit). / | ■> \Q A 
COMPLETE KIT «•■«»•■ WmV 

Carr. ami inn. 12/6. Ready wired 80/- 
extra. Illuminated perspex control 
panel. escutcheon. 7/6 extra. Four con- 
temporary mounting legs 6in. 10/6; 
flln. 11/6; 12in. 12/6 extra. 



TRANSISTOR 
COMPONENTS 

Midget I.F.'s— 465 Kc/s 9/16!n. 

diam. first, second or third. .5/6 
Osc. Coll M. * L.W. 9/16iu. dla. 6/- 

Mlclget Driver Trans. 9:1 6/- 

Mldget Output Trans. Push- 
Full— 3 ohms 6/- 

Eleot. Condensers— Midget typo 
1 mFd. -00 mFd. ea. 1/9, 100 mFd. 
2/-, 12V. Wkg. 

Condenser! 150 v. working 1 
.01 mFd., .02 mFd., .03 mFd- 
.04 mFd. 9d; 05 mFd.,. I mFd.,1/-; 
.25 mFd., 1/3; .5 mFd., 1/6, etc 
Midget Tuning Condensers. J.B. 
"OO" 208 pF and 176 pF. 8/6. 
ditto with trimmers, 9/6. J.B. 
220 pF and 105 pF cone slow 
motion 10/6. 365 pF single 7/6. 
Sub. min. fin. Dllcmln 100 pF, 
300 pF. 500 pF-. 7/- each. 
FERRITE AERIALS. M. & L.W. 
car aerial coil 9/3. 
Midget Vol. Control with edge 
control knob, 5 K/ohrus, with 
switch 4/9: Ditto less switch 3/9. 
Speakers: P.M.: 2ln. Plesscy 75 
ohms 15/6. 2; hi. Continental 8 
ohms, 13/6. 7 x 4ln. Plessey 35 
ohms. 23/6. 

Ear Plug Phones — Min. Con- 
tinental type 3ft. lead, Jack, plug 
and socket. High Imp., 8/-. Low 
Imp.. 7/6. 



Phono Plugs, 9d. Phono Sockets (open). 
9d. Ditto (oloiod), 1/-. Twin Phono 
Sockets (open). 1/3. 



RIMMERSi Ceramic (Compression 
Type)— 30pF, 50pF. 70pF. 9d.; 100pF/ 
ISOpF. 1/3; 250pF. 1/6: BOOpF 1/9. 
PHILLIPS. Bee Hive Type iconc air- 
spaced)— 2-SpF. 1/-; 3-30pF, 1/-. 
KNOBS — Modern Continental types 
Brown or Ivorv with Gold Centre; 
1- dia., 9d. e"ach: 1J'. 1/- each: 
Cone, knobs ivory with Gold Centre 
IS* dia. 8/9 per pair. Matching ditto 
2/6 ea. 

LARGE SELECTION AVAILABLE. 
METAL RECTIFIERS. STO Types— 
RM1, 4/9; RM2, 5/6; RMS, 7/6; 
BM4. 16/-; HMO, 21/-: RM1H. 17/6. . 

TUB-ELECTROLYTICS-CAN 
26/25V. 50/12v. 1/9; 8 + 8/450v. 4/6; 
50/50v. 100/125V. 8/- :32 - 32/275v. 4/6. 
8/450V. 4/350v. 2/3: 50/50/350v. 6/6. 
16 + 16/450V. 5/6; 60/250/875v. 12/6; 
32 + 3 2/450v. 6/6 ;100 I 200/276V. 18/6 



7 VALVE AM/FM RADIOGRAM CHASSIS 

Valve line-up ECC85. ECH3I. EF89, New 1965 Model now available 

EABC80. EL84. EM81. EZ80. •>*- 

Three Waveband and Switched Gram, 
positions. Med. 200-550 m. Long 
1 .1100-2.000 m. VHF/FM 88-95 Mc/s. 
Phillips Continental Tuning Insert with 
permeability t uning on FM and com- 
bined AM/FM IF trar-;;ormere. 400 
Kc/s. and 10-7 Mc/s. Dust core tuning 
all colls. Latest circuitry including 
AVC and Neg. Feedback. Three watt 
output. Sensitivity and reproduction 
of a very high standard. Chassis size 
13J x 61in. Height 7Jin. Edge illumin- 
ated glass dial llj x 3}in. 
Vertical pointer. Horizontal station names. Gold on brown background. 
A.C. 200/250v. operation. Magic-eye tuning. Circuit diagram now available. 
Aligned and tested ready for use £13.19.6. Carr. & Ins. 7/6. 
Comp. with Tape, O/P socket, ext. sp'k'r and P/U sockets and indoor F.M. 
aerial and 4 knobs— walnut or ivory to choice. 3tl P.M. Speaker only required. 
Recommended Qualltv Speakers 10' R.A., 87/6. IS,* x 8" E.M.I. Fidelity, 42/6. 
12" K.A. with cone. Tweeter. 42/6. Carr. 2/6. 




EXPANDED ANODISED METAL 
Attractive gilt finish Jin. x Jin. 
diamond mesh 4/6 sq. ft. Multiple* of 
6in. cot- Max size 4ft. x 3ft., 47/6, 
plus carr. Do., finer pattern mesh 
4/6 sq. ft., multiples of 12ln. max. 
size .lit. x 2 ft- 27/8 sheet. 

ENAMELLED COPPER WIRE— 
Jib. reels 14g-20g. 8/-; 22g-2Sg, 3/6; 
86g-3Sg, 4/9; 39g-40g. 6/-. etc 



TRS 



BONDACOUST Sneaker Cabinet Acoustic Wadding (1 In. thick approx.) 18 In. 
wide, iinv length cut, 2/3 per it.. 6/- per yard. TINNED COPPER WIRE, lfl-22g. 
4/. ji b. BRSIN MULTICORE SOLDER. 80/40 4d. per yard. Cartons 6d„ 1/-. 2/6 etc. 

TYGAN FRET or Vynair, 12 x 12m. 2/-; 12 x lain. 3/-: 12 \ 24ln. 4/-. etc. 

We manufacture all types Radio Mains Transf., Chokes, Quality O/P Trans., etc 
Enquiries invited for Specials. Prototypes for small production runs. Quotations 
by return. Scud for detailed bargain list, 3d. stamp. 

RADIO COMPONENT SPECIALISTS 

70 Brigstock Rd., Thornton Heath, Surrey. Boun: 9 a.m.-6 p.m.. 1 p.m.. Wed. 

1948 THO 2188. Terms C. W.O. or C.O.D. P041 and Packing up to t lb- 1/.; 1 (6. 1/9; 3 lb. 
»/.; 5 15. 3/8; 8 U>. 4/6. 



April, 1966 



PRACTICAL WIRELESS 



1023 



Circuits 'Diagrams* Repair Data 

Here's all you need for servicing 

OVER 

1450 Models 




Ace, Aerodyne, Ajax, Alba, Argosy, Baird, Berec, 
Bush, Cossor, Oansette, Oecca, Defiant, Doric, 
Dynatron, E.A.R., Ekco, Elizabethan, Elpico, E.M.I., 
Emerson, Eumig, Ever Ready, Ferguson, Ferranti, 
Fidelity, G.B.C., G.E.C., Grundig, H.M.V., Hitachi, 
Invicta, K-B., Magnavox, Marconiphone, Master- 
radio, McMiehael, Motorola, Murphy, National, 
Newmatic, Pam, Perdio, Peto Scott. Philco, Philips, 
Playmate, Portadyne, Portogram, Pye, Radio- 
mobile, Recording Devices, Rediffusion, Regentone, 
Retra, Revelation, R.G.D., Roberts' Radio, Sharp, 
Sinclair, Sobcll, Sonolor, Sony, Sound, 
Standard, Stella, Stereosound, Stuzzi, 
Teletron, Thorn, Trans Arena, U.K.W., 
Ultra, Volmar, Waltham-Standard, 
Zenith. 



(1962—1965) 

There is no other publication like Newnes 
RADIO & TV SERVICING ... the greatest 
time-saver and money-maker you can own! 
3 volumes packed with circuits, data and 
hints for repairing over 1,450 models 
(1962-65). TV, radio, tape recorders ... all 
the famous makes are here. Plus big 
section of latest Radio and TV develop- 
ments. Examine it, USE it for a week 
FREE! Don't miss this opportunity — 
simply post coupon today. Absolutely no 
obligation to buy! 

•TELEVISION* RADIO 
• RADIOGRAMS 
•TAPE RECORDERS 
•RECORD REPRODUCERS 



3 VOLUMES 
1,848 PAGES 



OVER 2,000 CIRCUITS & DIAGRAMS 




ONE REPAIR JOB 

CAN REPAY ITS COST 

Compiled by a team of research engineers 
this big 3-volume library gives you, instantly, 
the vital data and circuits you need. Cuts out 
guesswork and delays, steps up your earning 
power. 

Nearly 60,000 Sets of previous editions sold ! 
Are you missing extra income ? Find out why 
this big servicing aid is in such demand — 
send for your Free Trial Set today. 



I! 



If under 21 your father must fill up coupon. 
To: George Newnes Ltd., 

15-17 Long Acre, Fl ,„ Name 

London, W.C.2 (block letters) (Mr., Mrs., Miss.) 

Please send RADIO & TV 

SERVICING (3 volumes) Address ; 

without ob ligation to buy. 
If you accept this appli- 
cation I will post 10/- •■• 

deposit 8 days after 

? n Ceipl ° f , Ki° 0kS ; the " Occupation 

20/- monthly for a r 

months, paying £8. 10s. 

in all — or return the Signature 

books. Cash in u days 

. fr ce Trial applies G.8. For Ireland send cash 

._ iiy-fc Dr 'ce (relundable if title returned in Sdays). 
HilMla Overseas send cash pike plui 13 - p. & p. 



Tick V where <JW>/i'coM« 

The address en left l»— 


My Prooerty 


Ruled unfurnished 


Parents' Ham 

rurr.iir-.ed aCOOO). j~ 


Temporary iMress | 



1024 



PRACTICAL WIRELESS 



April, 1966 



LITESOLD SOLDERING INSTRUMENTS 



SEVEN SIZES, FROM 10 WATTS TO 55 WATTS. 



REPLACEABLE BITS, COPPER & PERMATIP. 
EXCELLENT TEMPERATURE REGULATION. 
COOL, UNBREAKABLE HANDLE. 
RAPID HEATING. 




LITESOLD 
instruments 
are compact and 
nicely balanced. 
Bits are spring-collet 
mounted for firmness 
and easy removal. Copper 
bits are standard, in sizes from 
■&" to |f* dia. PERMATIP bits are 
slightly slower, but eliminate bit face 
wear. LITESOLD elements are encased 
in specially pre-oxidised wire for constant 
temperature regulation from new — less 
glamour but honest design, also apparent in the 
simple, unbreakable handle, with the element unit 
secured by two self-tapping screws (servicing couldn't 
be easier) and firm, spring-on clip. LITESOLD hollow- 
spindle construction prevents heat loss into the handle 
(which DOES stay cool) and improves performance. Useful 
LITESOLD accessories include HEAT GUARDS for elements, and 
BENCH STANDS. 



Free details of the whole wide range of LITESOLD and ADAMIN soldering equipment in brochure SPIO. 

LIGHT SOLDERING DEVELOPMENTS LTD., 

28, Sydenham Road, Croydon, Surrey. Telephone: CROydon 8589. 



SIMPLE SERVICING. 
ALL VOLTAGES. 
LOW COST. 



soudogaz Blowlamp 

for the 
handyman 

Modern, clean 
and efficient... 

Ready for instant use at the strike of a match, operated 
by expendable 200 cartridge, gives instantaneous heat 
at 2198°F. (1200°C.) for approximately 2* hours. 
With the three accessories, solderings on lead, bronze, 
silver, zinc, and aluminium, electrical installations, 
defrosting pipes, paint stripping, gutter repairs, etc., 
can be quickly completed. 

SOUDOGAZ Blowlamp 45/- (Comp- 
lete with normal Jet Burner), 200 
Cartridge 3/9 extra. Paint Stripper, 
Fine Jet, Soldering Iron each 9/- 
extra. 

CAMPING GAZ INTERNATIONAL 

DIVISION 
P.T.C. South Street, Dorking, Surrey 





HEYJ ENLARGED EDITION 

of the popular 

GUIDE TO 

AMATEUR 

RADIO 

An invaluable guide 
for those new to 
Amateur Radio. 
The book, which 
contains a wealth of 
interesting and help- 
ful information, is 
of great assistance in 
obtaining a trans- 
mitting licence. 
Several new constructional projects have been 
added to this Eleventh Edition. The -Guide has 
88 pages, well illustrated with photographs, 
circuit diagrams etc. 

Price 5'- (by post 5'6) and 80 cents post paid in U.S.A. and 
Canada. 

Further details of other R S G B publications, information 
about membership of the Society, including a free copy 
of the monthly RSC B BULLETIN, and the book itself 
may be obtained from the publishers: 

RADIO SOCIETY of GREAT BRITAIN 

Dept. PW, 28 Little Russell St., London, W.C.1. 




April, 1966 



PRACTICAL WIRELESS 



1025 



Brand new individually 
checked and guaranteed 

VALVES 



AC/HL 476 
ACP4 6/- 
AC6PEX 5/- 
AL60 5/- 
ARP3 3/- 
ARPia 2/6 
ARP24 3/6 
AK8 8/- 
ARTP1 6/- 
ATP4 2/3 
ATP7 5/6 
A17 58/- 
AZ31 9,'- 
B6H 16/- 
BD78 40/- 
BL63 10/- 
B84 8/- 

B85 20/- 
>'s-4 st/r 

B2134 16/- 
BT19 25/- 
BT35 28/- 
BT43 150/- 
BI83 35/- 
CCai. 21- 
CL33 9/- 
CV71 8/- 
CV77 5/- 
CVI02 1/- 
CVI03 4/- 
<VI004 7/- 

cmu 7/- 

GV4015 5/- 
OV40S5 10/- 
IV4049 6/- 
CY31 6/6 
Dl 1/6 

D41 6/- 

DB1 6/- 

D77 8/3 

ll'ASO 12/8 
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UJ>41 4/- 
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DF73 5/- 



DL96 8/- 

DI.SIO 8/-' 

DL819 16/- 

ES0P 28/- 

E88CC 12/- 

E90CC 10/- 

EI14S 2/6 



EF85 
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kf'.m 
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BF90 

EPiee 



K1268 60/- EF184 
E1415 30/- EUT1 300/- 
E1524 12/6 ! EI.32 3/8 
EA50 1/- I EL34 
El 73 7/- • EUll 
EABC80 8/6 EL38 



K3A 30/- QP21 6/-IV1924 20/- 1 3X2 8/- 1 6F8G 

KT3C 22/- QP25 6/- . VMP45 12/- 1 4C87 35/- 6F12 

KT32 8/- QP230 6/- VP23 8/- 4D1 4/- 6F13 

KT33C 6/- 0.895. 10 8/6 VP133 8/- AA173G 5/- ! 3F14 

KT44 5/8 Q8150;15 VR89 8/- 



10/- 

u. 

17/6 

w« 

si- 
s/- 

8/- 
6/3 
5,'- 
S<- 
4/6 

KL380 20/1 ' |ct88 
BM80 6/- ESSS 

5*81 7/8 &,[!; 



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sua 

LOO 

EL81 
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Kl.-i 
E I,-.. 
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7/6 I F'fi063 
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EF37A 71- GfiO/SG 5/- 
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2/6 (I Ml 45/- 
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8/- I H68 7/- 

7/6 IIK64 22/8 
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KT63 il- 
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15/- 

?;- 

B/- 
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7/- 
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=/- 
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PCC89 10/- 
6/6 
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EM84 6/3 , P ^, ?! 
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EN 1 .74 80/- |gSS W 



10/- VRUi5,'306/- 

Q31202 8/- VR 150/306/- 

QV04/7 8/8 VV33A 4/- 

R3 8/- V1'39 61- 

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80/- VX8122 5/- 

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8UJ0P 15/- YV21 6/- 

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36/- 



TTR31 45/- 
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vis 



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PUS 
PL81 
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DS6 
027 

I ,-,ii 
053 
0191 
I" 801 



70/- LBSS 80/- 

6/- IC5GT 8/- 

18/- I 1DSGT 8/- 

8/- 1E70 7/6 

1P2 8/- 

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llrl 2/6 

1LA6 8/- 
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11-114 

is-jin 
LN4S 

IN 70 



go/> 

8/- 

s/- 

»• 

11/- 
11/- 

8/- 1 R.'i 

4/6 IH4 

4/6 IBS 

11/8 III 

18/- ' v 

UABT80 6/- SB26 

UAF49 9/- ■..•! 38 
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UBF80 8/6 2C34 
L-BF89 6/8 
VB1.21 11/- 
6/6 
S/- 



7!- 
5/- 
6/- 

6/6 , , 

P 1,500 15/- |-,-,' s "-. 

PM24A 5/- ,,,,;:, 

reu io/- i , :; « 

SSM l<« [,?& t'r. 

7/B lcI>3 10/ . 
14/-,l-F41 7/- 

8/6, UW1 

0/6 UL--I 

5/6 uue 



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P.V4 

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3A4 



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16/- 
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9/- 

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ton 

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ana 



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128C7 4/- , 446A 

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21 110 



5/- ---:i 
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6/- 811 

15/- , 813 

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28 V 5 8/- 

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30 6/- 

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5726 




37 


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8060 




88 


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6064 




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6065 


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8080 


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67 


6/- 


7475 


«/- 


58 


«/- 


8013A 


88/- 


69 


6/- 


8020 


8/- 



M.TJA 

883 

843 

.SiWA 



1012 
IK 16 
1316 
1K25 
I «M 
1099 
2051 



22;6 
8/- 
8/- 
22/8 
65/- 
35/- 
50/- 
4/- 
45/- 
16/- 
5/- 
14/- 
10/- 
4/8 
2/8 
21- 
61- 
4/- 
6/- 
3/- 
8/- 
6/- 
3/- 
4/6 
5/ 



Ilil.'lC 18/6 

4n«:i 8/- 

78180 30/- 

5704 9/- 



«f'97 350/- 
Special - 
Valves 
ACT6 £8 
K301 M 
KRN3A 

£3.10.0 
1B24 25/- 
2.J22 £2.10.0 
2.154 08 

41 7 A 30/- 
3J/03/B 

£37.10.0 
714AY £4 
725A 80/- 
726A 19/- 
Transistors 
'""■'■ 20/- 



OC22 
OP25 
OC44 
OC45 
OC71 

OOI9 

OCS1M 



28/- 

12/- 
61- 

o/- 
4/6 
6/- 
10/- 
II- 



"■ -•■ :o/- 

Of-122 16/- 
OOSM 10/6 
XC141 10/- 
XC142 15/- 
XC155 20/- 
XC156 22/6 
2NS02 47/- 
2X247 9/6 
2X5S5 10/6 
2X1090 20/6 
2X1091 29/- 



H.R.O. SENIOR TABLE MODEL 

TYPE 5A with "S" meter and crystal 
filter in excellent fully checked and 
tested condition together with set of 8 
general coverage coils and mains P.S.U. 
£33. Carriage and packing 30 -. 
Ditto, but model "M" £28 Carriage and 
packing 30/-. 

INSET MICROPHONE for telephone 
handset 2/6. P. &. P 2,-. 

DUMONT MODEL 241 OSCILLO- 
SCOPE in fully working condition 
£22.10.0. P. & P. 30;-. 

CR.ISO/2. Frequency coverage 1 .5-22 Mc/s 
in 4 bands. Price £31. Carriage 30'-. 

P.C. RADIO'S mains P.S.U. for above, 
90'-. 

VARIOMETER for No. 19 set, 17/6. 
P. & P. 3'-. 



MARCONI TF 868 UNIVERSAL 
BRIDGE. Capitance IpS to IOOu.S, 
inductance lu.H to I00H, resistance 
.1 ohm to 10m ohms. Q .1 to 10. Power 
supply Il5/230v A.C. In new condition 
with instruction book. £65. Carriage 30'- 

EVERSHED MEGGER CIRCUIT 

TESTER. 2 ranges to I.OOOii, I00II 
to 200.000U. With test leads, leather 
carrying case. Tested £4.19.6. P. & P. 3'6. 



PANEL METERS (round) 
500mV 3i' DC 32'6 

500mV* 3i* DC 35'- 

500mA" 2i' DC 22'6 

500 microamp 3i" AC 22'6 

500 microamp* 2" DC 19'- 

0-500 microamp 2i" DC 22'6 

25-0-25 m A 2," DC 45'- 

150-0- 1 500mA 3 J DC 29'- 

0-S00mV 3f DC 32'6 

0-I5V 2- AC I7'6 

0-50V 2f" DC 28'- 

0-1 50V 2j* AC 24'- 

"Projection type. 

MARCONI SIGNAL GENERATOR 
TYPE TF 801 B 3 S. Frequency range 
12-485 mes in five ranges. Directly 
calibrated frequency dial. Output wave- 
form: CW sinewave A.M.. pulse A.M. 
(from ext. source only). Internal modu- 
lation frequency 1,000 c/s. Output: A 
normal — continuously variable directly 
calibrated from 0. lu.V-0.5v. b, high; up 
to Iv. modulated or 2v. unmodulated, 
output impedance 50 ohms. Fine fre- 
quency tuning control, carrier on/off 
switch, built in crystal calibration for 
2 mc s and 10 mc/s. Stabilised voltage 
supply. In excellent "as new" condition, 
fully checked and guaranteed. £115. 
Carriage 30'- 



P.C. RADIO LTD 

170 GOLDHAWK ROAD, W.I2. 

ihepherd's Bush 4946 
Open 9-5.30 p.m. Thursday 9-1 p.m. 



THERMAL PLUS MECHANICAL 
CIRCUIT BREAKER FOR A.C. & D.C 

Current I amp. Protects against shorts 
(instantaneous cut-out at approximately) 
8 amps) and against overloads: 1.8 amp 
30 second, 2.1 amp 15 seconds, 2.5 amp 
8 seconds. Delayed cut-off may be ad- 
justed to different currents and times. 
Separate pair of contacts to indicating 
device. Dimensions 34 x If x -& in. 
Price I2'6. P. & P. 2'6. 
SEMI-AUTOMATIC BATTERY 

CHARGER "Baby Esstron". Initial 
charging rate 3.5 amps DC automatically 
reducing to 1.5 or lower (depending on 
specific gravity of battery acid). As the bat- 
tery receives the charge indication lights 
indicate visually the high current or when 
incorrectly connected. Meter incorporat- 
ed. For 6 or I2v. batteries. Mains voltage 
200,'240v. A.C. Price £3. P. & P. 4/6. 
AR88D RECEIVERS Fully reconditioned, 
£55, rebuilt models £85. Carriage paid U.K. 
TELEPHONE HANDSET. Standard 
G.P.O. type, new. 12'-. P. & P. 2'-. 
WIRELESS SET No. S2 (CANADIAN) 
Complete station consisting of Trans- 
mitter. Receiver, supply unit for 12v. 
All contained in special carrier. 1.75-16 
mc s in 3 bands. 813 as output valve. 
45-75w. phone and MCW. 70-100 watts 
CW. M.O. or crystal. Receiver includes 
crystal calibrator. Tx. can be exactly 
tuned to Rx. frequency. Noise limiter 
Sidetone. Loudspeaker on receiver with 
on- off switch. All brand new with acces- 
sories. Export. Price on application. 
Ditto, but Receiver only (without 
cabinet), £8.10.0. Carriage 20'-. 



1026 



PRACTICAL WIRELESS 



April, 1966 




1. MOTOR l U H.P. 1440 revs.. £2.10.0. '/j HJ. 1440 revs., £2.19.6. 
P. 4 P. 10/-. These have been removed from equipment but are 
fully guaranteed. 

2. CYLDON AM FM PERMEABILITY TUNERS FOR ALL TRANSISTOR 
OPERATION. Size '2J x 2J.ln. appro*. By famous manufacturer. A.M. 
I.F. 470 Kc/s, F.M.-I.F. 10.7 Mc/s. A.M. coverage from 1620 Kc/s-625 
Kc/s. P.M. coverage 108 Mc/s-88Mc/s. Circuit diagrams 2/6. FREE 
with Tuner, 1st. 2nd and 3rd A.M. I.F.'s, 1st, 2nd, 3rd and 4th F.M. 
I.F.'s VJ1.F. Osc. choke. A.M. I.F. trap. All the above are the R.F. 
end of an A.M./F.M. receiver car radio etc. The above items £2.10.0. 

3. AMPLIFIER KIT. 3 to 4 watt Ampifier Kit. Comprising chassis 8} x 
2\ x lin. Double wound mains transformer, output transformer, 
volume and tone controls, resistors, condensers etc. Valves 6T6, 
ECC81 and metal rectifier. Circuit 1/6, free with kit. 29/6 pins 4/6 P. 4 P. 

4. 8-WATT 5-VALVE PUSH-PULL AMPLIFIER 4* METAL RECTIFIER 
Size: 9 x 6 x ljin. A.C. Mains, 2O0-250v. 5 valves. For use with Std. 
or L.P. records, musical instruments, all makes of pick-ups and mikes 
Output 8 watts at 5 per cent total distortion. Separate bass and treble 
lift control. Two inputs, with controls for gram, and mike. Output 
transformer tapped for 3 and 15> ohm speech coils. Built and tested. 
£3.19.6. P. 4 P. 8/-. 

5. MAGNAVOX COLLARO. 8et of three Tape Deck Motors. These are 
made for 110v but suitable auto transformer Is supplied. Three 
motors 39/6. P. & P. 61- 

6. OSCILLOSCOPE lor D.C. and A.C. APPLICATIONS. Push-pull X 
amplifier; Fly-back suppression; Internal Time-base Scan Wave form 
available for external use; pulse output available for checking TV line 
O/P Transformers, etc. Provision for external — I/P and C.R.T. 
Brightness Modulation. A.C. mains 200-200v„ £18.18.0. P. 4 P. 10/-. 
FULL 12 MONTHS' GUARANTEE INCLUDING VALVES and TUBE. 

7. FIXED FREQUENCY SIGNAL GENERATOR. Crystal controls in metal 
case, size 10 x 6 x 6in. Incorporating two FC13 valves, mains trans- 
former, metal rectifier, choke, indicator, lamp, crystal and numerous 
components. Modulated and unmodulated output socket. Originally 
used for I.T.V. frequencies. Brand new. 39/8, plus 7/-. P. 4 P. A.C. 
mains 200-230 volts. 

8ILICON RECTTFIERS. 250v. PJ.V., 760mA. Sir lor 7/8 poet paid. 

8. POCKET MULTI-METER, Size 3| x 2* i l|ln. Meter site 2} x ljin. 
Sensitivity 1,000 O.P.V. on both A.C. and D.C. volte. 0-15. 0-150, 
0-1,000. D.C. current 0-lSOmA. Resistance 0-100kfl. Complete with 
test prods, battery and full instruct Ions, 42/8. P. 4 P. 3/fi. FREE GIFT 
for limited period only. 30 watt Electric Soldering Iron value 15/- to 
every purchaser of the Pocket Multi-Meter. 

9. CHANNEL TUNER I.F. 16-19 Mc/s. Continuously tunable from 174- 
216 Mc/s. Valves required— PCF80 and PCC84 (In series). Cover 
BBC and IT A ranges. Also Police, Fire and Taxis, etc Brand new 
by famous maker, 10/-, P. 4 P. 3/-. 

10. POWER SUPPLY KIT in metal case, size 31 x 2} x Sin. incorporating 
mains transformer, rectifier and condensers. 230/250 A.C. mains 
Output; 9v., 10mA. 10/8 plus 3/- P. & P. 

11. B.8.R. MONARCH UA16 WITH FULL FI HEAD, 4-speed, plays 10 
records, 12in.. 10in., or 71n. at 18, 33, 46 or 78 r.p.m. Intermixes 
7in., lOin. and 121n. records of the same speed. Has manual play 
position; colour brown. Dimensions: 12J x lOJin. Space required 
above baseboard 4Jin., below baseboard 2)10, Fitted with full Fi 
turnover crystal head. £4.19.6. P. 4 P. 7/6. 

12. FTRST QUALITY PVC TAPE 
S ) in. Std. 8S0ft. . . 9/- 
7in. Std. 1200ft. . . 11/8 
Sin. L.P. 240ft. . . 4/- 
5|in. L.P. 1200ft. . . 11/8 
7in. L.P. 1800ft. . . 18/8 
P. 4 P. on each 1/6. 4 or mon 

13. MAYPAIR 5-TRAN8ISTOR TAPE RECORDER 
Capstan-driven, battery operated, 7j and 3J l.p.s- Precision made. 
Push-button controls. "High quality 2|ln. speaker. Push-pull circuit- 
Output: 400 mw. Frequency response: 200-7,000 kc/s. Fast rewind. 
Up to 1 hour twin track playing time. Automatic erasing for re- 
recording. Dimensions: 8in. x llin. x 3Jin. Weighs only 71bs. £11.11.0 
plus 7/6 P. 4 P. 

14. 40W FLUORESCENT LIGHT KIT incorporating OEC Choke size 8} x 
lj x ljin. 2 bi-pin holders, starter and starter holder, 11/6. P. 4 P. 4/6. 
Similar to above: 80W Fluorescent Light Kit incorporating GEC choke 
size llj x ljin. 2 bl-pln holders, starter and starter holder, 17/8. 
P. 4 P. 6/6. 

16. GEC FLAT HEATER ELEMENT 500 w. 

Can be used for wash boilers, washing machines, etc. Five or six ele- 
ments can be used in parallel to give 2600 '3000 watts. Size 5J x 11, 
copper enclosed. 2/6 each, P. 4 P. 1/-. 4 or more Post Paid. 

RADIO & TV COMPONENTS (ACTON) LTD. 

21 b High Street, Acton, London, W.3. 

All enquiries Stamped Addressed Envelope 

Goods not despatched outside U.K. 

Shop hours 9 a.m. — 6 p.m. Early closing Wednesday 



Bin. UP. 850ft. 


. . 10/6 


3in. T.P. 600ft. 


. . 10/6 


Bin. T.P. 1800ft. . . 


.. 26/6 


SJin. T.P. 2400ft. . . 


. . 32/6 


Tin. T.P. 3800ft. 


.. 42/6 


Post Free. 





April, 1966 



PRACTICAL WIRELESS 



1027 



MUSETTE 



6 TRANSISTOR 
SUPERHET 




PRICE 

P. & P. 3'6~ 

Circuit diagram 2'6 
Free with parts. 

including carrying strap. 



39/6 



PORTABLE RADIO 



2±" Speaker. 

6 Transistors Superhet Output 
200mw. 

Plastic Cabinet in red, size 4J" x 3* x 
If* and gold speaker louvre. 
Horizontal Tuning Scale. 
Ferrite Rod Internal Aerial. 
IF 470 Kc. 

All components, Ferrite Rod and Tun- 
ing Assembly mounted on printed 
board. 

Operated from PP3 Battery. 
Full comprehensive instructions and 
point-to-point wiring diagram. 
Printed Circuit Board. 
Tunable over medium and long wave 
band. 
Car aerial and ear piece socket. 



NEW TRANSISTORISED 
SIGNAL GENERATOR 



^jf Mk II 




Site Si-* x 3i* x lj". For IF and RF alignment and AF output 
700 c/s frequency coverage 460 Kc s to 2 Mc/s in switched 
frequencies. Ideal for alignment to our 39/6 P '* ,P ' 



Elegant Seven and Musette. Built and tested. 



3'6 



&ve*t 



COMBINED PORTABLE and 
CAR RADIO 



The Radio with the STAR features 

■^- 4in. Speaker. 

■^t* 7-transistor superhet. Output 350mW. 

■£ Wooden cabinet, fitted handle with silver coloured 

fittings. Size I2£ x8|x 3£in. 
■^r Horizontal tuning scale, size 1 1£ x 2f in. in silver 

with black lettering. 
^r All stations clearly marked. 
■jlr Ferrite-rod internal aerial. 
■jit- I.F. neutralisation on each 

stage 460 kc/s. 
■Jc D.C. coupled output stage 

with separate A.C. negative 



ONLY 



£4.4. 



Plus 6'6 P. & P. Parts 
list & circuit diagram 
V6. FREE with parts 



feed back. 
A|l components: ferrite rod and tuning 
assembly mounted on printed board. 

•jfc- Operated from PP9 battery. 

■jlj- Full comprehensive instructions and 
point-to-point wiring diagrams. 




■fa Printed circuit board, back printed with all component values. 



POWER SUPPLY KIT to 
purchasers of "Elegant Seven" 
parts, incorporating mains trans- 
former, etc. A.C. mains 200-2S0v. 
Output 9v. 50mA. 7'6 extra. 

~k Fully tunable over medium and long waveband, 
-^r Car aerial socket. Full after-sale service. 



All enquiries Stamped Addressed Envelope. 



RADIO & TV COMPONENTS (ACTON) LTD 2IC High St., Acton, London W3 

Open 9 a.m.— 6 p.m. including Sats. Early closing Wed. Goods not despatched outs.de U.K. Terms C.W.O. 



1028 



PRACTICAL WIRELESS 



April, 1966 







-QUALITY 




ANOTHER CODAR TRIUMPH! 



THE NEW 1966 CR.70A 
COMMUNICATION RECEIVER 

This completely new receiver sots a new high standard for 
performance and finish unequalled at the price, ana is a worthy 
addition to the outstanding range of CODAR quality communi- 
cation equipment. Frequoncy range: o60 h.c/s-30 Mc/s (o40-iu 
metres) in four ranges: 560 Kc/s-1.5 Mc/s; 1.5 Mc/s-4.2 Mc/s: 
4.2 Mc/s-11.5 MC/S: 11.5 Mc/s-30 Mc/s. Slide rule scales fpr each 
band calibrated In frequencies plus an additional logging 
scale in degrees. Two speed vernier tuning control with reverse 
slow tune action. Unique aerial input stage exclusive to the 
CR.70A employing High Q ' Air-spaced CODAR-QOIL Inductor 
giving extremely high gain with low noise level. Panel aerial 
trimmer for peaking weak signals. Double tuned I.F. Iron 
cored transformers. 470 Kc/s with EF183 irame grid valve for 
maximum gain and selectivity. 5 valves (including two tw.n 
triodes) giving? valve lineup. Separate B.F.C\ stage for CW and 
SSB reception. Calibrated singal strength 'S meter, illumin- 
ated Automatic Volume control. Panel phone lack for 
1 •private" listening. 2-3 ohm output lor external speaker. 
Superb styling, metal cabinet in the new Organasol Satin lustre 
finish Size 13" x 5}" x 71'. For A.C. 200/250 v. Ready built. Not a 

Kit at the fa ntastic low price of £19-10.0. Carr. 7/6. 

CODAR R.F. PRE-SELECTOR MODEL P.R.30. Consider- 
ably improves the performance of any superh&t receiver over 
1.5-30Mc/s. Uses EF183 Frame Grid Valve, and provides up to 
20dB gain plus substantial image rejection, improved signal/ 
noise ratio and selectivity. Selector switch for either dipole or 
Single wire antenna. Power requirements 180-2o0 volts 12mA 
H.T. 6.3 volte. 3 amp L.T. Size 8J x 5 x4ln. Ready built, complete 
with cables, plugs and instructions. £5.10.0. Carr 3/6. MODEL 
P.R.30X. Self powered model for 2O0-250v. A.C. Also provides 
25mA at 200v. H.T. and 6.3v. 1 amp L.T. for other accessories 

£7.4.0. C arr. 3/6. 

CODAR "Q" MULTIPLIER MO DFX R.Q.lfl. For use with 
anv superhet receiver with an I.F. betwen 4o0 and 4(0 Kc/s. 
Provides considerable increase in selectivity lor either peaking 
or rejecting a signal on AM. CW. or SSB. BFO. Size 8J x o x 4in. 
Power requirements 130-250V. H.T. at 5mA 6.3y...3 amp L.T. 
Ready built complete with cables, plugs and instructions. 
£6.15.0- Carr. 3/6. MODEL R.Q.I0X. Self powered version for 
200-250V A.C. and also provides 25mA at 200v. H.T. and 6.3v. 1 

amp. L.T. f or other acc essories £8.8.0. Carriag e 3/6. 

HIDAR A.T.5. 12 WATT 2 BAND TRANSMITTER. The 
newest most compact transmitter for fixed or mobile use on 
160-80 metres. "The tiny TX with the BIG voice". Size only 
84 x 5 x 4in. (Base area is less than two-thirds of this page.) 
High stabilitv new type calibrated VFO. 1.8-2.0 Mc/s and 3.5-3.8 
Mcs (up to 4 Mc/s export). Air-spaced CODAR COIL Pi-net 
output, P.A. Plate current motor plus neon indicator. Plate- 
Screen modulator. AM/CW switch and Panel key lack. Plug 
change over for 6 or 12 volts heater supply. Ready built £16.10.0. 
Carr 4/-. A.T.5 POWER SUPPLY UNITS, For 200/250V. AC 
and 12v. Solid state for Mobile use. complete with all Transmit/ 

Receive chan geover s witching available. ^^^___ 

< ODAR-Kit CR.4SK MAINS T.R.F. SHORT-WAVE RE- 
CEIVER. World wide reception — North and South America. 
Russia. India. Australia, Far East, Amateurs, Shipping, etc. 

£ Separate electrical bandspread. * 3 slow motion vernier 
ives. -*Low loss polystyrene plug-in coils, factory aligned. 
•Dials calibrated in frequencies and degrees. * Power output 
3 watts for 2/3 ohm speaker. -ArValve line-up: ECC81. EL84, 
EZ80. Size 12 x 5J- x 7ln. CODAR-KIT CR.45K complete with 
valves, 3 coils (10-28, 25-75, 60-176 metres) and 11 page instruction 
manual. £9.10.0. Carr. 5/6. Extra coils 4/9 each. Instruction 
manual only 4/- (credited on order). (Can also be supplied 

ready built — price on r equest). , 

CODAR-Klt MINI-CLIPPER— OUR FAMOUS SHORT- 
WAVE RECEIVER +Can be built in one evening ready to 
switch on and bring the World to your flngertipsat very low 
cost. ^Supplied complete with valve, one coil 25-75 metres and 
4-page instruction manual. PRICE 39/6. Carr. 3/-. Extra Coils 
4/9 each. Instruction Manual only 21- (credited on order). 
Electrical Bandspread avaUable. Provision to add 2 transistor • 
amplifier. 



SEND 6d. IN STAMPS FOR ILLUS. LEAFLETS OF THE CODAR RANGE 



H.P. TERMS AVAILABLE 



WORLD-WIDE MAIL ORDER SERVICE 




CODAR RADIO COMPANY 

BANK HOUSE, SOUTHWICK SQUARE 
SOUTH WICK, SUSSEX. Tel. 3149 

G3IRE G3HGQ 

Canada: Coder Radio of Canada, Tweed, Ontario. 



PRACTICAL 

WIRELESS 



APRIL 1966 
VOL 41 NO 710 



LAW OF THE JUNGLE 

SOME readers take us to task for disapproving of pirate radio stations. A common 
accusation is that we are "against pop music"; that, teetering on the brink of senility, 
we cannot appreciate the prodigious talents of the Top Tenners. Such thrusts are wild 
indeed, for they completely miss the point! 

Whether they churn out pop music, symphony concerts, language tuition or talks 
on advice to the lovelorn is beside the point; they should not be on the air at all. 

Aircraft are not allowed to land and take off just where they fancy, flights must be 
controlled and scheduled — even though some of our critics claim that "the air is free 
for all to use how they like". Cars are not allowed to be driven at 100 mph in the wrong 
direction down a one-way street. This complex modern society insists that "liberty" 
must often be subjected to judicious control. And broadcasting is noexception. 
. Years of co-ordination and planning have made the jig-saw of the m.w. band fit 
together reasonably well. Frequencies, sites, power allocations have been arranged to 
the best mutual advantage. But the pirates burst in with a lofty disdain for law, order 
and the rights of other people to listen. Consequently protests have comefrom Sweden, 
Yugoslavia, Czechoslovakia, etc., concerning reception ruined by pirate stations. 

Pirates also evade the Copyright Act, to the financial detriment of authors, com- 
posers and musicians. There is no control of programme or advertisement content. 
There is nothing to stop undesirable elements setting up their own pirate station. 
Unless . . . 

The Government has, by implication, shown that the position of the pirates is 
indefensible. They are breaking international radio law. They are specifically contra- 
vening legislation signed last year by the Council of Europe — which other signatories 
have already used to shut down thejr pirates. Then what is the PMG waiting for — 
could it be a General Election! 

Let him no longer tolerate the law of the jungle in broadcasting. 



CONTENTS 

News and Comment 

Direct Reading Frequency Meter 

Switch-Tuned Superhet — Part 2 

On the Short Waves 

Books Reviewed 

E L Key 

Practically Wireless 

Versatile Preamplifier and Tone Control 

Reflex 2 

No. 19 Set Mods.— Part 2 

Mic Preamp 

Electronic Gate or Trace Doubler 

Oscillator Circuitry — Part 2 

Club Spot— Y.M.C.A. Belfast 



1030, 1060 
by K. Royal 1032 

by F. L Thurston 1036 

by John Gutthdgc and David Gibson, G3JDG 1040 

1044 
by P. Murphy 1047 

by Henry 1052 

by A. S. Ellis 1053 

by Gordon J. King 1056 

by S. Simpson 1062 

by A. E. J. Simons 1070 

by H. T. Kitchen 1073 

by R. Ley land 1082 

1089 



All correspondence intended for the Editor should be addressed to: The Editor, "Practical Wireless", George Newnes Ltd., Towsr House. 
Southampton Street, London, W.C.2. Phone: TiMple Bar 4363. Telegrams: Newnes Rand London. Subscription rates, including postage: 
29s. per year to any part of the world. © George Newnes Ltd.. 1966. Copyright in all drawings, photographs and articles published in 
"Practical Wireless" is specifically reserved throughout the countries signatory to the Berne Convention and the U.S.A. Reproductions 
or imitations of any of these are therefore expressly forbidden. The MAY ISSUE WILL BE PUBLISHED ON APRIL 7th 






1030 



A New P.W.? 



I read Practical Wireless 
with great interest and would like 
to see you enlarge it. I would 
also like to see a Practical 
Wireless Annual (similar to the 
Practical Motorist Annual). 

One other thing I would like to 
see is the revision of the Practical 
Wireless Circuits book, as 1 think 
this is very out of date — the coils 
and components being almost 
impossible to obtain. 

I would like to see a licence 
for Novice Amateurs on 160m 
using I0W. as I think it would 
make use of a band which is dead 
most of the time. 
J. Savage. 

London, 
S.E.I 1. 
• • • 

[Practical Wireless will be 
"going up in size" from the 
.May, 1966 issue onwards, and 
Practical Wireless Circuits is, at 
the moment being revised and 
will contain up-to-date circuits 
using up-to-date components. It 
will be on sale in a few months 
time.] — Editor. 

Correspondents' Club? 

I have noticed that there are 
several enthusiasts about my own 
age (14) who have written to 
P.W. asking for correspondents. 
I am sure that we could all get 
together and have regular corres- 
pondence, writing say, each 
month or fortnight to each in 
turn. By doing this, we would 
gain the experience of others and 
also offer our own experience, 
some, like me, no doubt are pre- 
paring for the R.A.E. and would 
certainly benefit from corres- 
ponding with other enthusiasts. 

Another idea I had was to 
swop components for stamps or 
other articles with enthusiasts in 
India, Ceylon, etc.. who find it 
difficult to obtain electronic com- 
ponents and issues of P.W. 

If anyone is interested would 
they please write to me. 1 will 
then write to all the members 
giving the the names and adresses 
of the other members to start the 
" Pen Club " off. I would wel- 
come any other ideas on the sub- 
ject. 
S. V. Odgear. 

Ml The Hollow, 

Corsley, 

Warminster, 

Wiltshire. 



IMEWS AND.. 



P.W. AND P.TV. FILMSHOW 




Friday, 4th February, was the date of the P.W. Filmshow. Once again 
this year, the meeting was well attended by readers from all parts of 
the country. 

In the absence of Mr. Stevens, the Editor, Mr. A. T. Collins, the 
Managing Editor of the Practical Group took the chair. After his opening 
speech, Mr. Collins introduced Mr. Ian Nicholson, of Mullard Ltd., the 
speaker of the evening. 

Mr. Nicholson then introduced the first film, entitled "Electro- 
magnetic Waves — Part 2". After this film there was an interval of 25 
minutes during which refreshments were served. 

During the second half of the programme, Mr. Nicholson gave a talk 
on Servicing Transistor Receivers. After this, there followed a film 
entitled "Thin-Film Microcircuits". The evening ended with a question 
and answer session during which Mr. Nicholson answered questions put 
to him by members of the audience. 

The photograph shows Mr. A. T. Collins (left) and Mr. Ian Nicholson 
discussing a thin-film microcircuit. 

AIRBORNE RADIO AIDS FOR EAST AFRICAN VC-10S 
Three Super VC-10 aircraft on order for East African Airways are 
to be completely equipped with Marconi Sixty Series airborne 
radio navigation and communication aids, including the Doppler 
Navigator, which will form the primary en-route navigational 
system in the aircraft. 

Each aircraft will be fitted with dual installations of the ADI60 
v.h.f. communications system, AD260 v.h.f. navigation system, 
AD360 automatic direction finder and the aircraft selective 
calling system, Selcal. Also in each aircraft will be the Marconi 
Doppler navigator, type AD560. 

The AD560 Doppler navigator is currently in operation with 
BOAC, Qantas Airlines, Ghana Airways and Air New Zealand 
and will be fitted in new aircraft for Iraqi Airways and Pakistan 
International Airways in addition to the Anglo/ French Concorde 
supersonic airliner. 



.COMMENT 



ARCOLECTRiC RELEASE NEW CATALOGUE 

Arcolectric Switches Ltd., Central Avenue. West Molesey. Surrey, 
announce their 1966 catalogue, No. 136. It describes their current 
range of switches, neon indicators, and signal lampholders. 

Many new products are featured in this catalogue including the "27" 
and "28" range of lever and semi-rotary switches. 

Copies of this catalogue are readily available upon request to Arco- 
lectric Switches Ltd. 

HARLOW MOBILE RALLY 
The date of the Harlow and District Radio Society's Annual 
Mobile Rally will be Sunday, 25th September, 1966. Further 
details available from Hon. Sec, G. O'Donald, G3TLJ, "Great 
East", Harlow Road, Roydon, Harlow, Essex. 

PETO SCOTT AMENDS NAME 

Peto Scott Electrical Instruments Ltd. has changed its name to Peto 
Scott Ltd. It is thought that the former title gave a too restricted view 
of the wide range of activities now carried out by the company. The 
field of operation now extends through black and white and colour 
studio and professional television installations, professional tape 
recording, video tape recording, sound systems, functional music 
machines, Eidophor large screen television projection, language 
laboratories, teaching machines, schools TV equipment and overhead 
projectors. 

SPACE ORDER FOR MARCONI 




Marconi Co. Ltd., is currently building three space communications stat- 
ions which are to provide the first British military satellite communications 
system. These stations are to take part in a joint project with the American 
military authorities, using a series of near-synchronous satellites launched 
by America. 

This photograph, taken at one of the Marconi Company's experimental 
sites near Chelmsford, shows the 40ft. diameter dish aerial for the second 
station. It is seen here, fitted on a temporary mounting for test purposes. The 
white dome in the background is the 60ft. high inflatable radome into which 
the aerial will shortly be moved. The radome will provide full weather 
protection for the aerial, its fully steerable mounting, and for some of the 
associated equipment. 

more News and Comment 



1031 

The Meaning of Amateur 

I hope the attitude of Mr. 
Davidson, G3FG (page 939. 
March issue) is not typical of the 
majority of radio enthusiasts. 

I fully endorse the remarks of 
your Birmingham correspondent 
who G3FG criticises and would 
suggest that G3FG is being 
narrow-minded. It is. I think, 
possible to distinguish two sepa- 
rate hobbies (closely connected, 
I admit) i.e. set construction and 
DX (be it ham or broadcast DX). 
I myself could not really care 
who or what constructed my set 
as long as it gives me some DX. I 
know that some friends of mine 
will willingly construct a set and 
"home brew" it but once they 
get it working and calibrated, 
give no thought to the matter, 
take the set to pieces and start on 
a different circuit. 

As to the meaning of " ama- 
teur" I hardly think it is relevant 
to either hobby. The thing that 
disturbs me most, from what I 
read of your correspondence, is 
the unwillingness of some — not 
many — to accept newcomers, 
novices not versed in the habit of 
set construction. 
P. Charlton. 

Middlesbrough. 
Yorkshire. 

Single Circuit Panels 

I was intrigued by W. 
Groome's approach to the prob- 
lem of assembling printed cir- 
cuits without messy chemicals. 
(P.W. Feb., 1966). I wonder why 
he assumes that copper cladding 
has to be used? 

I, as an "old timer" faced by 
this modern chassisless age — 
have found a simpler approach! 

I use 22 s.w.g. copper wire! 
What's more, on top of the board 
my essemblies look identical. Just 
as small and just as neat. 

The only special tool needed is 
wire-bending pliers, to put neat 
loops on the ends of each link. 
The wires can run point-to-point 
by judicious use of bits of sleev- 
ing (though they needn't). 

It's a lot easier to perform 
mods and de-bug new designs! 

When finished, a layer of 
lacquer holds all in place . . . 
(Most times, surplus flux does all 
that is needed). 
R. G. Young. 

Peacehaven, 
Sussex. 

on page 1060 






A 

Direct 
Reading 



Frequency Meter 



• Described by K. Royal 




THBidevice about to 'be described commenced 
life in the author's laboratory for the measure- 
ment of the pulse repetition frequency of an 
oscilloscope's timebase in terms of a direct read- 
ing analogue on a milliameter. This simply means 
that the milliameter is scaled directly in terms of 
frequency instead of current. The meter circuit 
thus has to translate frequency to a direct-current 
value. Moreover, to be of much use it has to do 
this in a linear manner without progressive com- 
pression or expansion of the scale. That is, any 
change in applied frequency should give a corres- 
pondingly linear change in current reading over a 
specific frequency range. 

The device then graduated to a " tachometer " 
for checking the speed of car engines, and finally, 
to a meter for indicating the frequency of any 
audio signal, whether of square, pulse or sine 
wave. 

Frequency Discriminator 

The key to the whole thing is a rather special 
frequency discriminator* whose circuit is given in 
Fig. 1. This is how it works. When the input signal 
goes negative, capacitor CI charges through the 
signal source resistance, through Rl and through 
Dl. With Dl connected the way round shown on 
the diagram is, of course, in forward conduction 
on a negative-going signal, while the emitter 
junction of the transistor Trl is in reverse conduc- 
tion. 

As long as the time constant Cl/Rl is short 
(also assuming a low impedance or resistance 
source), CI stores an electric charge equal to CV. 
where C is the value of the capacitor and V is the 
amplitude of the input signal. 

Now, when the input signal changes to positive 
(or zero), CI discharges through the emitter base 
junction of the transistor and a pulse of current 
flows in the collector circuit. This happens on each 
cycle of signal,; and since CI discharge currenl is 
-equal to-. C\5#^where t is a time function of the 



cycle and is itself equal to 1 /f, where f is the repe- 
tition frequency, it follows that the average emitter 
current is CVf. The average collector current is 
thus CVst, where a is the current gain. 

In the common base mode, a is almost equal to 
unity (actually it is less than unity because the 
emitter current is equal to the collector current 
plus the very small base current) so the 
average collector current can be considered 
to be CVf. From this, then, it can be seen that the 
current is proportional both to frequency and the 
value of CI. The frequency range over which the 
discriminator will function is thus influenced by 
the value of CI. Table I relates maximum 
frequency to value of CI. 

In Fig. 1 a milliammeter is included in the 
collector circuit, and this is scaled to read 
frequency direct. It is possible to employ a high 
resistance voltmeter instead of a current meter by 
putting a resistor in series with the collector and 
using the voltmeter to indicate the voltage in terms 
of frequency developed across it. In this case, the 
voltage as recorded would be equal to CVfR, 
where R is the value of the collector resistor. 

Input Limiter 

The basic circuit in Fig. 1 is dependent upon the 
signal source impedance and amplitude, and is thus 
somewhat unpredictable. For more consistent 
operation a " buffer " stage should be interposed 
between the signal source and the discriminator, 




Fig. I : Circuit of the basic frequency discriminator. 



April, 1966 



PRACTICAL WIRELESS 



1033 



with the buffer acting also as an amplitude limiter. 

A practical arrangemeni in this context is given 
in the circuit in Fig. 2. Here Trl is the buffer/ 
amplitude limiter. It serves virtually as a switch- 
ing transistor the input signal performing the 
switching action. This is how it works. 

On a negative-going input signal current flows 
in the emitter/base junction of Trl causing a 
flow of current in the collector resistor R3 and the 
voltage at the collector to fall. On a positive going 
input signal, the base is made positive with respect 
to the emitter and no current flows in the collector 
resistor and the voltage at the collector rises 
almost to the supply voltage. During this half- 
cycle, however, Dl conducts and maintains a con- 
stant mark/space ratio. That is, the transistor is 
switched on and oft for equal periods of time. 

A square-wave is thus developed at the collector 
of Trl. and since the amplitude of this wave is 
held constant by the transistor bottoming when the 
input signal swings negative and cutting off when 
it swings positive, amplitude limiting occurs provi- 
ded the input signal amplitude is itself sufficient 
fully to switch the transistor as described. Thus, 
any increase in signal input amplitude does not 
influence the amplitude of the square-wave signal 
at the collector. 

The signal, then, is of ideal form to work the 
frequency discriminator which, in Fig. 2. is Tr2, 
with C2 as the charging capacitor. A preset resistor 
is included in series with Tr2 collector and milli- 
ammeter to set the current for full-scale deflection 
at the top frequency it is required to indicate. 



Unit Construction 

This circuit, in fact, was used by the author both 
to indicate the pulse repetition frequency of the 
timebase of an oscilloscope and to determine the 
turnover speed of a car engine by "counting" the 
number of pulses produced by the contact breaker 
of the ignition system, the scale of the milli- 
ammeter then translating these direct to revs per 
minute. 

The circuit was built upon a small piece of 
" Eyelet Board " measuring about 2^ x 2|in. The 
special "eyelets" (see the Component List) are 
secured in the holes corresponding to the compo- 
nent lead-out wires. The wires, along with the 
circuit connecting wires themselves, are then 
soldered to the eyelets. 

A word or two about the eyelet board would not 
be amiss at this juncture. The board itself is made 
of a resin-bonded laminate and the eyelets are of 
tinned brass. The laminate is perforated every 
0-2in. and the holes (which are about -nrin. in 
diameter) tightly accommodate the eyelets. These 
are prevented from being pushed right through the 
holes by a slightly raised flange at" one endT This 
also gives a little clearance for winding round the 
circuit connecting wire. 

The eyelets are fitted to the selected holes by 
inserting the barrel up to the flange, turning the 
board over and then gently tapping the protruding 
barrel end with the tip of a centre punch. One of 
the automatic press-type punches allows this 
operation to be handled swiftly and accurately. 



Meter Connection 

Fig. 3 shows how the board is processed to 
accommodate all of the components of the circuit. 
These are wired together underneath the board 
and connection to the meter terminals is accom- 
plished by the positioning of eyelets close to two 
holes made in the board to take the terminals of 
the meter. Each hole thus has one meter connect- 
ing eyelet close to it, as shown in Fig. 3. Washers 
placed on the meter terminals after they have been 
pushed through the holes in the board thus provide 
good electrical connection between the adjacent 




Fig. 2 (above): Circuit of the instrument described in the 
text. 

Fig. 3 (below) : Layout of components on the eyelet board. 



Eyelets tor meter terminal 
connections 



Holes fop 
meter terminals 






1-ArHiK 

■ Svleter 




■L ■ 

! C~J 1> ojo + o\ h o;o o 

Y, \ -4— -P- --'-*•- — • 

^•iafc. ..••""o* o A o] o o o 6 



i&fe. 



eyelets and the terminals when the terminal nuts 
are tightly screwed down. In this way, therefore, 
the module is secured to the meter movement. 

The 1mA meter movement employed by tho 
author had its own mounting case and this easily 
accommodated the meter-mounted module with 
room to spare for a small PP3 or PP4 battery if 
required. The author's prototype is externally 
powered so no on/off switch was fitted. However, 
a switch would be needed should internal battery 
powering be adopted, since the limiter takes a 
small quiescent current of just under 1mA. 



1034 



PRACTICAL WIRELESS 



April, 1966 



The front view of the instrument, with the scale 
calibrated in pulses per second, is shown in the 
heading photograph. The two top terminals accepi 
the input signal and supply positive, to which the 
input signal is relative while a small terminal on 
the rear of the case picks up supply negative. 



TABLE 


1 


Maximum Frequency 


Value for C2 


100 c/s 
1 kc/s 
10 kc/s 

100 kc/s 
1 Mc/s 


1 ,*F 

0-1 /iF 

001 aiF 

0001 p? 

0001 jiF 



Table I : Showing maximum frequency for variations ofC2. 

As mentioned earlier the instrument was made 
originally to indicate timebase repetition frequen- 
cies of an oscilloscope up to a maximum of 8kc/s. 
For this application, a value of 0-OljuF was found 
suitable for C2 (see Table 1). After setting the 
timebase to 8kc/s as determined by a calibrated 
audio oscillator, the preset R4 should be adjusted 
to give a deflection of 8 on the meter. A signal of 
any frequency below 8kc/s is then read directly 
from the scale. 

As a Rev-counter 

For use as a car engine rev-counter, the pulses 
as developed between the contact breaker (CB) and 
switch (SW) terminals of the ignition coil are 
applied to the instrument. The pulses here have a 
rate proportional to the engine speed. For a four- 
stroke engine, the frequency is equal to engine 



To'CB'on 
Ignition coil 



_ To 'A' 
(Fig. 2) 



Pulse 
input 



;r2a 
•7kn 



.To'B* 

■ ( Fig. 2) 

Fig. 4 (above): Circuit of input attenuator required for 

indicating ignition pulse rate. 

Fig. 5 (below): Circuit ofzener diode stabilisation. 



To negative . 
point on module 



To positive 
point on module 



^y Zener 

JCAZ207 + 



TO "SW" on coil 



4. To car chassis 
\- (only if positive 
is^Earth") 

turnover speed in revs per minute X n/120, where 
n is the number of cylinders. Thus, such an engine 
running at, say, 3,000 r.p.m. produces a pulse rate 
of 100 c/s, while a single cylinder, four-stroke 
motor-cycle engine will produce a pulse rate of 
only 25c/s at the same turnover speed. 

A top engine speed of 6.000 or 8,000 r.p.m. is 
generally conventional depending really on the 
nature of the engine. Thus, the value for C2 is 
usually in the order of 1/tF, but for single cylinder 
engines a value up to 4,uF may have to be used. 
The value in these cases is best determined by 
experiment for the least ripple effect on the needle 
at low revs. 




Rear view of finished instrument showing completed 
circuit board. 

It is not safe to apply the contact breaker pulses 
direct to the circuit since their large amplitude 
could damage the semiconductors. An attenuator 
after the style of that shown in Fig. 4 circuit 
should be used at the input. The rev-counter may 
be powered either by its own, internal battery (as 
may be required for some motor cycles without 
battery powering) in which case the " pulse input " 
point is connected to "CB" on the ignition coil 
and the supply positive line of the circuit is con- 
nected to the metal of the engine or car body, or 
powering can be from the car battery. 

In the latter case, the car supply voltage must 
be stabilised, as this has a tendency to rise and fall 
with engine revs and with varying loads on the 
electrical system. 

The best stabilising element for this application 
is the zener diode. When this kind of diode is 
biased for reverse conduction it becomes a rela- 
tively low resistance at a Specific value of reverse 
voltage, called the " zener voltage". The current 
then passed by the diode is called the "zener 
current ". Under this condition, the voltage 
developed across the zener diode remains substan- 
tially constant over a range of input voltages. This 
means, then that the voltage across the diode is 
stabilised. 

A zener diode stabilising circuit is given in 
Fig. 5 and " R " in series with the supply and the 



Fig. 6: Circuit of com- 
mon-emitter amplifier 
for increasing the sensi- 
tivity of the instrument, 
as described in the text. 




^ 



April, 1966 



PRACTICAL WIRELESS 



1035 



COMPONENTS LIST 

CIRCUIT FIG. 2 
Resistors (all £-watt carbon insulated^ 

Rl 47k Q 

R2 220k Q 

R3 4-7kii 

R4 lOkQ preset (printed-circuit board type) 
Capacitors 

CI 0-5^F I2v 

C2 (see Table I) 
Semiconductors 

Trl and Tr2, OC7I 

Dl and D2, OA8I 
Meter Movement 

Moving-coil 0-1 mA 
Sundries 

Eyelet Board and eyelets (available from Messrs. 

R. & E. Lamb, 17 Queens Road, Leytonstone, 

London E.I I. Connecting wire, battery (PP4) 

and battery clips. Instrument case. 



CIRCUIT FIG. S 
Resistor 

I50Q I -watt 
Semiconductor 

Zener diode, OAZ207 





CIRCUIT FIG. 6 


Resistors (all ^-watt carbon, insulated) 


Rl 


56k ii 




R2 


22 k Q. 




R3 


5-6kQ 




R4 


2-2kQ 




Capac 


tors 




CI and C3 4^F, 


I2v. Electrolytic 


C2 


lOOuF, 6V 


. Electrolytic 


Semiconductor 




Trl, 


OC7I 





diode sets the zener current. The value is deter- 
mined by the required k>ad current, the supply 
voltage and the type of zener diode used. The 
manner of connecting to the car is revealed in 
Figs. 4 and 5. This applies only to cars with 12V 
supplies and positive earths. 

The main application of the device, of course, is 
as a direct reading frequency meter, and the way 
that it can be used to indicate engine revs may be 
of academic interest only to some of our readers. 
Nevertheless, the versatility of the device is 
revealed. 

To provide a frequency indication from low- 
level signals, an amplifier is required in front of 
the main circuit of Fig. 2. A suitable amplifier is 
given in Fig. 6. This is just an ordinary common- 
emitter circuit, but the lift that it gives to signals 
is sufficient to allow the device to respond to sig- 
nals as low as 50-100 mV. When this amplifier is 
used, Rl and CI from Fig. 2 circuit should be 
omitted. m 

* D. E. O'N. Waddington, "A Simple Frequency/ 
Voltage Converter " Marconi Instrumentation, 
VoL 10 No. 1. 



JUST OUT! 



HOUSEHOLDER 

acnjmual iaee 



«aW?08*S&BASS€StiiP 
Yfltlfi BWS WQRKSHOP 




NEW PROJECTS, NEW IDEAS, 

NEW WAYS 

TO IMPROVE YOOR HOME 

Go for the 1966 practical householder 
annual today. It brings you dozens of 
ways in which you can give your home an 
up-to-the-minute new look .... with 
detailed instructions and how-to-do-it 
illustrations that show you how to tackle 
each job with a sure professional touch. 
Don't miss it. 

SPECIAL SECTIONS ONi 

HOME WORKSHOP 

SOLVING THE GARAGE PROBLEM 

KITCHEN FURNITURE YOU CAN BUILD 

GUIDE TO HOME HEATING 

GATES AND FENCES FOR HOME AND GARDEN 

BUILDING A GLAZED SUNL0UNGE 

REFERENCE DATA FOR ROOFING MATERIALS 

AND CONCRETE 

BUILDING AND WOODWORKING 

SIMPLIFIED ELECTRIC WIRING 

BIG DEMAND -GET YOURS NOW! 

2/6 NEWSAGENTS AND BOOKSTALLS 



A x>aili 

id 

u 




SUPERHET 



PART 2 



STAGE 3— AERIAL AND PRE-SE LECTOR 
SECTIONS 

A 10 x -gin. ferrite rod is used in the aerial, 
which is home wound. While this is 
recommended, it is not essential, and a ready- 
made type of aerial may be used if preferred. The 
winding and mounting details for the home-made 
type axe shown in Fig. 5. Note that the aerial is 
aoounted directly on the speaker. 

Secure the external aerial ,'a.g.c. socket in place 
at the rear of the chassis, checking that there are 
no shorts to chassis. Secure L3 in place above 
chassis. 

Secure S2 in place.* Ft will probably be 
necessary to make this switch up by modifying 
an alternative type, and the essential dimensions 
are given in Fig. 6. Such a conversion is not 
difficult: a multibank switch, at least as long as 
that shown, is obtained. The switch must have at 
least 4-ways. The switch is then dismantled, 
reduced to the correct length, and re-assembled 
to conform to Fig. 6. If too many -'ways'' are 
available, they can be reduced to the correct 
number (4) by drilling and tapping a 6BA hole 
in the switch front to take a short 6BA screw 
which will act as a stop. 

When the switch has been secured in place at 
the front of the chassis, secure the trimmer 
capacitors in place, as shown in Fig. 6. The 
method of mounting the beehive trimmers is 
shown in Fig. 7. where it can be seen t^at t^ev 
are soldered to the drilled-out ends of 2 BA 
screws, which are then bolted directly to the 
chassis, using a solder tag in place of a normal 
washer. 

Now wire-up the circuit as shown in Fig. 6. 
Use screened leads where indicated. Check the 
wiring and switch on. Test vol 'sees are VI. anode 
250V, screen 145V, cathode 1.5V. 



*S2 can be made to order by: Special : st 
Switches Ltd., 79a Duke Road. London. W.4. 
Price approximately 17/6. Drawings must be 
supplied with order. 



F. L. THURSTON 



TESTING 

Temporarily connect a germanium diode in 
circuit with one end to the loose end of CIO 
(audio input) and the other end to the grid of 
VI. Switch S2 to position 3. The ferrite aerial 
and diode are now connected as a simple crystal 
set. If the volume control is turned full up, 
the Light programme should be heard reasonably 
well. By adjusting C23 it should be possible to 
tune the programme in quite sharply, although 
the Home will probably be heard as well. 

Now disconnect the diode from VI grid and 
connect it to tag 2 of the 16-way tag strip. The 
circuit is now connected as a t.r.f. receiver. When 
S2 is switched to position 3 it will be seen that, 
by adjusting C23 and C26 together, the Light can 
be tuned in far more sharply than before, that 
interference from the Home is greatly reduced, 
and that the Light now comes in with vastly 
improved strength. By connecting an external 
aerial (a few yards of wire into the external 
aerial socket, the signal strength is increased even 
more. 

The trimmer capacitors should now be aliened 
in conjunction with positions of S2, as follows: 

Position 1 — (Radio Caroline). Tune C21 and 
Slug of L3. 

2 — (Luxembourg). Tune C24. 
3— (Light). Tune C23 and C26. 
4— ' Home). Tune C22 and C27. Fixed 
padder. 
Note that the above tuning sequence must be 
followed. The stations on positions 1 and 2 may 
be very weak. 
This concludes stage 3. 

STAGE 4— OSCILLATOR AND MIXER 
SECTIONS 

Secure L4. the oscillator coil in place below the 
chassis. This coil is sold as a short-wave 
oscillator coil, to cover the 90 to 250 metre bands. 
At the particular frequencies used in th ; s rece'ver, 
this coil gives a better L/C. ratio, and therefore 
better frequency stability, than would a normal 
medium-wave oscillator coil. 



April, 1966 



PRACTICAL WIRELESS 



1037 



Secure the small variable 
capacitor C32, in place at 
the front of the chassis. On 
the prototype, this variable 
has a maximum capacitance 
of about l5pF. 

Secure the three Phillips 
" beehive " trimmers in 
place, as shown in Fig. 8. 
Solder the lOOpF postage 
stamp trimmer, C28, 
between the insulated stator 
terminal of C32 and chassis. 

Wire-up the circuit as 
shown in Fig. 8, noting 
where temporary connec- 
tions are made. Use screened 
lead where indicated. The 
diagram gives the wiring 
details for the Voltage 
Regulator, the Oscillator, 
the Cathode-Follower and 
the Mixer. 

TESTING AND 
ALIGNMENT 




/i.\ Screened lead 
to main aerial 
winding 



Screened lead'^i ='£ "= = = = = = = =/= = = = = == = ===V 

to external / 

aerial winding Chassis cut-out for speaker 



Check the wiring and if 
satisfactory insert the valves 
and switch on. Check the 
voltages as shown in Fig. 1. 
If all is well, connect one 
end of a capacitor of about 
•01/*F value and 300 volts 
working to the pin of i.f.t.l 
which goes to pin 5 of V2, 
the mixer. To the free end 
of the capacitor connect a 
germanium diode (GEX 34), 
and connect the other end of 
the diode to the free end of 
CIO (input to a.f. section). 
Set the upper tuning slug of 
i.f.t.l so that it is just below 
the top of the can. 

The receiver as so far 
constructed, consists of a 
superhet with a pre-ampli- 
fier and a single i.f. stage, 
followed by a detector and 
a.f. amplifier. 

The set must now be lined 
up. The r.f. stages have 
already been approximately 
aligned to the four required 
stations in stage 3 of the 
construction. It remains to 
finalise their alignment and that of the oscillator. 

Switch S2 to position 1, and set the front panel 
trimmer, C32, to mid position. Set tuning slug of 
L4 half in and lock. Now adjust C28, the lOOpF 
trimmer mounted on C32, until Radio Caroline 
is heard at maximum strength. There should ')e 
no trouble in receiving this station. Now re-tune 
C21 and L3 slug for maximum signal. Once set, 
these three trimmers will require no further 
adjustment. Switch to position 2 of S2, and adjust 
C29 for Radio Luxembourg, then re-trim C24 
for maximum strength. 



Note:— A' indicates insulating tape, Vindicates Terry clips 
Fig. 5: (above) Aerial winding and mounting details 
Fig. 6: (below) Layout and wiring details for stage 3 of construction. 
16-way tag strip 



TO 

external aerial 

socket (SKT2) 

mounted on 

rear of 

chassis 




* See text 



Spindle 



—41 



*E'=Earthed solder 
tag 



C21 (50pF postage stamp trimmer, 
mounted to chassis front) 



Repeat for the Light, using C30 for the 
oscillator, and C23 and C26 for r.f. stages, in 
switch position 3. Finally, switch to position 4, 
and adjust C31 on the oscillator and C22 and 
C27 at r.f. for the Home. Note that, should it 
not be possible to tune in using the components 
specified, adjustments can be made by adding or 
reducing parallel tuning capacitance. This com- 
pletes the r.f. and oscillator alignment. 

Now remove the capacitor connected to the 
primary winding of the i.f. transformer, and 
connect it to the secondary winding (pia of Lf.Ll 






1038 



PRACTICAL WIRELESS 



April, 1966 



with no leads soldered 
to it). Adjust the 
lower tuning slug of 
i.f.t.l for maximum 
signal (any position 
of S2 may be used). 
Now re-trim upper 
tuning slug, and 
finally re-train lower 
slug again. The 
primary of i.f.t.l is 
now fully aligned, 
while the secondary 
may be considered to 
be temporarily aligned 
(it will require re- 
trimming after the 
two additional i.f. 




Phillips 

'Beehive' 

trimmer 



'Beehive' 
soldered Into hole 
<? An 2BA bolt 

2BA bolt with 
head sawn off and 
hole drilled In one 

end to take 

'Beehive' 



2BA tag 
washer 



-Chassis 



A=2BA securing nuts 
Fig. 7 : Method of mounting 
the beehive trimmers. 

stages are added in stage 5 of the construction). 

EXPERIMENTS WITH THE MIXER/OSCIL- 
LATOR SECTION 

As constructed, the circuit used for the mixer 
gives very low noise, while the oscillator is 
exceptionally drift free and immune from 
"pulling". By making temporary alterations to 
the circuits, it is possible to demonstrate quite 
forcibly the inferiority of some alternative circuits. 
Space is limited, however, and only two experi- 
ments will be given, as follows: 

If a small transistor radio with built-in aerial 
is available, place it near to the oscillator coil 
(L4) and tune through the medium waveband; a 
number of whistles will be picked up. demonstrat- 
ing that the oscillator is working. Tune in to one 
of these whistles, and then move 
the transistor set to the r.f. coil, 
L3; the whistle will still be there, 
but will be very weak. Finally, 
move the transistor set to the 
ferrite aerial; if any whistles are 
still available they will be very 
weak indeed. 

Now unsolder the lOOOpF 
capacitor. CI 8. from pin 2 of V2 
(mixer cathode) shown as a tem- 
porary connection in Fig. 8. 
Solder a 15pF capacitor between 
pin 1 of V3 oscillator anode) and 
pin 1 of V2 (mixer grid). The cir- 
cuit is now connected as a mixer 
with the oscillator injected to the 
grid, quite a common circuit. 

If the transistor set is now 
placed near the r.f. coil, L3. 
whistles will be heard far more 
strongly than was formerly the 
case. Whistles will also be heard 
at the ferrite aerial. It may be 
noted that if a superhet is made 
without a pre-selector stage, using 
oscillator injection to the mixer 
grid as is often done the resulting 
"receiver" will in fact act as a 
quite effective transmitter! 

Another point may be demon- 
strated with this circuit, by 
pressing a finger against the 



mixer grid pin; a quite considerable reduction in 
volume will be noticed. This loss of volume can be 
attributed to loading and de-tuning of oscillator 
and r.f. stages. If the circuit is now rewired to con- 
form to Fig. 8 (the " temporary " connections can 
now be made " permanent ") and the same finger 
test is made to the point of injection (mixer 
cathode), it will now be found that no reduction in 
volume takes place. This is because both the oscil- 
lator and r.f. stages are isolated from the point of 
injection, and also because no loading of the actual 
injection voltage takes place due to the low impe- 
dance used. 

The mixer gives very low noise and good gain, 
and an essential part of the design which makes it 
possible to obtain these results is the voltage divi- 
der and decoupling network, R3-R4-C3, which 
feeds a constant and predetermined voltage to the 
mixer screen grid; the screen grid voltage must be 
within 5V of that shown in Fig. 1. An effective way 
of demonstrating the importance of this voltage 
is to replace R3 with a variable resistor of about 
100 to 250kXl value, and adjusting the value while 
monitoring the screen grid voltage: it will be found 
that as the voltage departs from that specified, the 
noise increases and the gain decreases. Many con- 
ventional mixers are found to have the high noise 
and low gain that is associated with this test. 
Once the circuit has been re-wired to conform to 
Fig. 8, stage 4 of the construction is complete. 

STAGE 5— I.F. SECTIONS 

Wire up the circuit as shown in Fig. 9. Check 
wiring. Switch on and check voltages as shown in 
Fig. 1. 



denotes earthed 
solder tag 

m connections of R3 
and C18 denotes that 
these are made initially 
as temporary only. 
See text 




Wafer "c" 



Wafer "b" 



red tag 



f 



Screened lead to 
C32 (on front of chassis). 
Connect lead to stator 
terminal, screen to earth. 
Ensure that rotor is earthed 

* See text 

Note: Solder C28 (XOOpF postage stamp trimmer) 
between stator and earth terminals of C32 



Fig. 8: Wiring and layout for stage 4 of construction. 



April, 1966 



PRACTICAL WIRELESS 



1039 



NOTE. Points marked X in Fig. 9 are tem- 
porary connections only. 

ALIGNMENT. Disconnect the capacitor used 
in aligning stage 4 from the secondary of i.f.t.l. 
and reconnect to the primary of i.f.t.2 (connected 
to pin 5 of V5). Adjust the primary tuning slug for 
maximum signal, then re-trim secondary of i.f.t.l 
again, and finally re-tune i.f.t.2 primary again. 
Alignment of i.f.t.l is now complete. 

Move the capacito.' to the secondary of i.f.t.2, 
and repeat the above procedure with the primary 
and secondary tuning slugs of i.f.t.2. When align- 
ment is satisfactory, move the capacitor to the 
primary of i.f.t.3, and align the secondary slug of 
i.f.t.2 and the primary slug of i.f.t.3. To complete 
the tuning, move the capacitor to the secondary of 
i.f.t.3 and trim the primary and secondary windings 
of that i.f.t. 

Note that, because of the use of three i.f. stages, 
the tuning is so sharp that it will probably be 
necessary to de-tune the i.f.'s slightly if acceptable 
quality audio is to be received. 

Stage 5 of the construction is now complete. 

Note :-'X' temporary connection only. 
IF.J.Z 




tJJpCjSJT* ^cejA^' 



Fig. 9: Wiring and layout for stage 5 of 
construction 



STAGE 6— DETECTOR AND A.G.C. 

The permanent detector and filter network can 
now be connected into the circuit. 
Remove the temporary detector circuit used in the 
two preceding stages (the capacitor and diode). 
Wire up the circuit as shown in Fig. 10. 

The dimensions of the component board shown 
are approximate only; as an alternative to the 
board, the components may be soldered to suitable 



1F.T.3 



To chassis 




: :C6 



To loose end 

'W*M - otC10 



(input to 
A^amp) 



Fig. 10: Wiring and layout of detector filter. 

miniature tag strips. When completed, the circuit 
is switched on to test that it is working correctly. 

If working satisfactorily, wire up the a.g.c. 
circuit as shown in Fig. 11. Note that the "tem- 



porary ** connections of Fig. 9 are removed and 
re-wired as "permanent ones as in Fig 11. After 
checking over the wiring, switch on and select a 
station. The a.g.c. circuit may result in some small 
loss in volume compared to that obtained earlier; 
the stations should now, however, be virtually free 
from " fade ". 



To AGC socket 
IFT2 1 e V6 

° ® * /: 

5§kil ® m 

o © 




IFT3 



o e • s 



C19 



Fig. 1 1 : A.G.C. wiring. 




If a voltmeter is available it can be connected to 
the a.g.c. socket provided at the rear of the chassis. 
The a.g.c. voltage is negative, and rises in magni- 
tude with the strength of the i.f. signal. Thus, as a 
signal fades, so the a.g.c. voltage will fall. The 
voltage will vary between about zero and 5V 
(measured with a v.t.v.m.), the normal amplitude 
being about 4V. 

The tuning of the r.f. oscillator, and i.f. stages can 
be perfected if required, by using the a.g.c. point 
as a tuning monitor. 

The construction of the receiver is now complete. 

THE CABINET 

The prototype receiver was placed in a simple, 
close fitting cabinet, which was suspended below a 
cupboard in the kitchen, as shown in the photo- 
graph. This cabinet may be a trifle small for really 
good, cool running of the radio, and the reader 
may prefer to make a similar cabinet but of larger 
dimensions. Quarter-inch or heavier ply-wood is 
used in the construction. The sides and top and 
base are cut to the required size and nailed and 
glued together. A fairly rough form of construction 
can be used, as any mistakes are " camouflaged 
when the unit is finally covered with rexine. 

Before proceeding further with this " box " sec- 
tion of the cabinet, make up the front panel and 
check that it fits correctly to the radio. When 
making the front panel, allow for the thickness of 
the speaker gauze that will be used to cover it, and 
the thickness of the Rexine used to cover the 
" box ", when working out the overall dimensions. 
When the front panel is correctly cut, cover its 
front and sides with the selected speaker gauze, 
gluing it in place with " Copydex " adhesive. 

Now place the Rexine selected to cover the 
" box " in position, and after trimming, glue (using 
Copydex) the Rexine to the front edge and inside 
only. When the glue has set (about 10 minutes) 
push the completed front panel in place in the box, 
peel back the Rexine layed on the box, and secure 
the front panel in place with a few light nails, 
hammered in from the outside of the box. 
Finally, complete the cabinet by glueing the 
remaining Rexine in place. 



on the 

Short Waves 

MONTHLY NEWS FOR DX LISTENERS 



All times are in G.M.T. 



All frequencies are in kc/s. 



The Broadcast Bands— by John Guttridge 



CONTRIBUTIONS have been lighter than usual 
this month. Don't forget we want your news. 
Thanks go to J. McNally, S. Haagensen, S.B.C., 
A. J. Jenkins, Middlesbrough Boys High School S. W. 
Club, I. Black and P. A. Church. 

Algeria: Radio Algerie (21 Boulevard des Martyrs, 
Algiers) now has English from 2200—2230 on 6,175/ 
890. Same outlets are used for Spanish 2230—2300 
and French 0630—0830 and 1700—2200. French is 
also carried from 1200—1700 (0900—1700 Sundays) 
or 890/11,835. Report forms are now available from 
this station which now gives full QSL verification. 

Congo: Radiodiffusionde la Republique Democrat ique 
du Congo, (B.P.3171, Leopoldviile) has been heard in 
French at 1900 on the new frequency of 9,780. Local 
dialect follows at 1927. 

South Africa: South African Broadcasting Corpor- 
ation (P.O. Box 8606, Johannesburg) now carries the 
Africa service at 0300—0400 on 6,150/7,270, 1000— 
1600, 15,220/17.805; 1600—1710,4,975/15,220/17,805, 
1710—1845, 4,975/1 1,900'15,220; 1845—2000, 4.975/ 
9,525/11,900; 2000—2100, 4,975/7,270/9,525; 2100— 
2115 7,270/9,525. On Sundays transmissions start at 
1100 and 17,805 changes to 11,900 at 1650. One of 
the stations new 250kW outlets is used on 4,975. At 
2000 11,900 carries the programme Radio Paradys. 

Tunisia: Radiodiffusion Television Tunisienne (139 
Avenue de Paris, Tunis) is now carrying the home 
service on the new frequency of 6,305. 

Burma: Burma Broadcasting Service (Prome Road, 
Kamayut P.O., Rangoon) can be heard from around 
1300 to sign off at 1345 on 4,795. 

Japan: N.H.K. (Tokyo) can be heard with English 
around 1300 on 9,525, though there is interference 
from Voice of America, Greenville, in Spanish to 
Latin America on the same frequency. 

Lebanon: Lebanese Broadcasting Station (Radio 
Lebanon, Ministry of Orientation, Information and 
Tourism, Beirut) has been reported back on 1 1 ,770 
to Africa from 1830—2030 (English 1830—1900). 
Reception in England is good. 

Papua and New Guinea: Radio Rabaul (P.O. Box 71, 
Rabaul, New Britain) uses 3,385 from 0600—1300.. 
Sends acknowledgement folder. Radio Kerema (Gulf 
District, Papua) on 3,245 from 0720—1100. Radio 
Daru (Western District, Papua) on 3,304 from 0800— 
1100. Radio Goroka (Eastern Highlands, New 
Guinea) on 2,410 from 0800—1100. 

U.S.A. Voice of America (US Information Agency, 
330 Independence Avenue, S.W. Washington 25, DC), 
will use the following frequencies to Europe in 
English from March 6. 3,980 (Munich) 0300—0730, 
1400—2345; 5,965 0300—0730, 1630—2200, 5,995 
(Greenville) 0300—0730; 6,040 0500—0700; 7,200/ 
7,250 0330—0730; 7,205 1500—1900; 7,210 1900— 



2245; 9,540/9,740/15,295 0430—0730; 9,565 1830 — 
2245; 9,760 1700—2245; 11,760 1830—2215; 15,205 
(Greenville) 1400—2215; 15,290 1400—2000; 17,780 
(Greenville) 1400—1800; 1,196 (Munich) 1600—1830. 

Netherlands Antilles Trans World Radio (Bonaire) 
has English at 2100 in the 25m.b. Frequency is believed 
to be 11,840. 

Argentina Radiodifusora Argentina al Exterior 
(RAE), (Sarmiento 151, Buenos Aires) now carries 
English from 2300—2345 and not 2400 on 11,710. 
The programme has also been occasionally heard on 
11,780 and 9,690. After close down of the Inter- 
national service at 0030, 11,710 is reported to carry 
the National Service. 

Brazil: The following stations are available in the 
early evening: Radio Mayrink Veiga (Rua Mayrink 
Veija 15, Rio de Janeiro) on 11,770; Radio Sociedad 
de Bahia (Rua Carlos Gomes 57, Sa Ivador, Bahia) 
on 11,875; Radio Tupi (Avenie Venezuela 43, Rio 
de Janeiro) on the new frequencies of 11,705/9.800; 
Radio Bandeirantes (C.P.372, Sao Paulo) on 11,925; 
Radio Brasil Central (C.P. 330, Goiania) on 11,815. 

Denmark: Radio Denmark, (Radio House. Copen- 
hagen V) may reintroduce the programme "Short- 
waving to the World" on Saturdays at 1015 — 1100 
on 9,520. On March 6, 15,165 replaces 9,520 for the 
1 730— 1810 transmission. 

German Federal Republic, Deutsche Welle (Bruedes- 
strasse 1, Postfach 344, 5 Koln) now uses 9,575/7,175 
for the 0300 — 0340 English transmission. 

German Democratic Republic, Radio Berlin Inter- 
national (Berlin-Oberschonweide, Nalepastrasse 18- 
50) uses the additional frequency of 5,300 in its 
English European transmission at 1730. Other 
frequencies are 6,080/6,115/7,185/7,300/9,730. There 
is a new transmission at 1815 on 1,511. 

Great Britain, Manx Radio (P.O. Box 22, Douglas, 
Isle of Man) is understood now to have a power of 
2kW. After dark uses 1,594. 

Hungary: Radio Budapest ' (Brody Sandar — S.U. 
5-7 Budapest VIII) has English to Europe on 5,900/ 
7,220/7,305 from 1930—2000 and 2200—2230. The 
2200 transmission is also carried on 6,234. English to 
North America is at 0030—0100, 0130—0230 on 
9,833/9,540/7,220/6,234 and 0300—0400, 0430—0500 
on 9 833/7,220/6,234/5,900. 

Portugal: Radio Lisbon, (Rua Sao Marcal, 1-A, 
Lisbon) reported using 7,285/7,130/6,185/6,025/5,975 
for English to Europe at 2015—2100. 

Egypt: Cairo Radio (UAR Broadcasting and TV 
Maspero, Cairo) now carries English to Europe at 
2100 — 2215. Frequencies are 9,475/11.915. 

Saudi Arabia: Saudi Arabia Broadcasting (Ministry 
of Information, Airport Road, Jeddah) puts in .a 
strong signal after 2200 on 7,220 but suffers from 
Budapest on same frequency and a jammer on 7,215. 



April, 1966 



PRACTICAL WIRELESS 



1041 




NOT BUILD ONE OFOUR 
PORTABLE TRANSISTOR 



RADIOS... 



BACKED BYOUR SUPER AFTER SALES SERVICE 



All components used in out 
receivers may be purchased 
separately if desired. Parts price 
lists and easy build plans avail- 
able separately at prices stated. 
Overseas post /0/-. 



FIRST FOR QUALITY, PERFORMANCE & PRICE! 
NEW ROAMER SEVEN Mk IV 

7 WAVEBAND PORTABLE OR CAR RADIO 
Amazing performance and specification ir Now with PHILCO MICRO.ALLOY R.F. TRANSISTORS 

FULLY TUNABLE ON ALL WAVEBANDS • 9 stages— 7 transistors and 2 diodes 

Covers Medium and Long Waves. Trawler Band and three Short Waves to approx. 15 metres- 
Push-pull output for room tilling volume from rich toned T x 4' speaker. Air spaced 
ganged tuning condenser. Ferrlte rod aerial for M & L waves and telescopic aerial for S waves. 
Real leather look case with gilt trim and shoulder and hand straps. Sl7e 9 x7 x 4in. approx. 
The perfect iiortalile unci the ideal car radio. (Uses PP7 batteries available anywhere). 
-* EXTRA BAND FOR EASIER TUNING Total cost of partsnow only £C I Q 1 P. & P. 



O F PI RATE STATI O NS etc Parts Price List and easy build plans 3/- (FREE with kit) 



5/6 




MELODY 
SIX 



". . . amazed at volume and 
performance . . . lias really come 
up to my expectations " 
S.G. Stockton-on-Tees. 
9 8 stages — 6 transistors 
and 2 diodes 

Our latest completely port- 
able transistor radio covering 
medium and long waves. 
Incorporates pre-tagged cir- 
cuit board. 31n. heavy duty 
speaker, top grade transis- 
tors, volume control, tuning 
condenser, wave change slide 
switch, sensitive 6in. ferrlte 
rod aerial. Push-pull output. 
Wonderful reception of B.B.C. Home and Light, 208 and 
many Continental stations. Handsome leather-look pocket 
size case, only 61 x 3} x liin. approx. with gilt speaker grille 
and supplied with hand and shoulder straps. 
Ports Price List and Total cost of all £J O ft p - * p - 




eosy build plans 2'- 
(FREE with kit) 



parts now only 



3/6 



POCKET FIVE 



>des 




7 stages — 5 transistors and 2 di 

Covers Medium and Long 
Waves and Trawler Band, a 
feature usually found In 
only the most expensive 
radios. On test Home, Light. 
Luxembourg and many 
Continental stations were 
received loud and clear. 
Designed round supersensi- 
tive Ferrlte Rod Aerial and 
fine tone 2iin. moving coil speaker, built into attractive 
black case with red speaker grille. Size 51 x 11 x 3Jln. (Uses 
1289 battery available anywhere). 
Ports Price List and easy build plans 1/6 (FREE with kit) 
Total cost of all A"} If. 
parts now only ^*/ ° P. & P. 3'-. 

NEW ROAMER SIX 

NOW WITH PHILCO MICRO-ALLOY R.F. TRANSISTORS 
• 6 WAVEBAND I ! 

B 8 stages — 6 transistors 
and 2 diodes 

Listen to stations half a 
world away with this 6 
waveband portable. Tune- 
able on Medium and Long 
waves. Trawler band and 
two Short Waves. Sensi- 
tive ferrlte rod aerial and 
telescopic aerial for short 
waves. Top grade transis- 
tors. 3-inch speaker, 
handsome case with gilt 
fittings. Size 7J x5J x Uln. 
Carrying strap 1/6 extra. 

* EXTRA BAND FOR EASIER TUNING OF LUX, ETC. 

eosy build plans 2'- , £J. | y.O ■>/(, 

(FREE with kit) par " now only J 6 





NEW TRANSONA 

PIWET "Home. Light. A.F.N., 
| Vt Lux. all at good volume." 
G.P. Durham. 
% 7 stages — 5 transistors and 2 
diodes 
Fully tunable over Medium and Long 
Waves and Trawler Band. Incorpor- 
ates Ferrlte rod aerial, tuning con- 
denser, volume control, new type fine 
tone super dynamic 2}in. speaker etc 
Attractive case. Size 81 x 4J x liin. 
with red speaker grille. (Uses 1289 battery available anywhere.) 
Total cost of all A") If. P. & P. Parts Price List and easy build 
parts now only "■*/•» 3 / 6 plani 2 I. (FREE with kit) 

TRANSONA SIX 

8 stages— 6 transistors and 2 
diodes 

This Is a top performance receiver 
covering full Medium and Long 
Waves and Trawler Band. High-grade 
approx. 3in. speaker makes listening 
a pleasure. Push-pull output. Ferrite rod 
aerial. Many stations listed in one even- 
ing Including Luxembourg loud and 
clear. Attractive case in grey with red 
grille. Size 6i x ii x ltin. (Uses PP4 
battery available anywhere.) Carrying 
strap 1/- extra. 

Total cost of all CO If. P. & P. 

parts now only J*/" 3^6. 

Ports Price List and easy build plans 1/6 (FREE with kit) 





SUPER SEVEN 

# 9 stages — 7 transistors and 2 
diodes 

Covers Medium and Long Waves 
and Trawler Band. The ideal radio for 
home, car or can be fitted with 
carrying strap for outdoor use. 
Completely portable — has ojilt-ln 
Ferrlto rod aerial for wonderful 

reception. Special circuit incorporating 2 R.F. Stages, push-pull output. 

3in. speaker (will drive large speaker). Size 7( x 5j x liin. (Uses 9v. 

battery, available anywhere.) 

Total cost of all {"> IO f. P. & P. Parts Price List and easy 



parts now only 



3/6 



build plans 2/- (FREE 
<vith kit) 



RADIO EXCHANGE CO 

61, HIGH STREET, BEDFORD 
Telephone: Bedford 52367 

Callers side entrance Barratts Shoe Shop open 9-5 p.m. Sats 1 0- 1 2.30 p.m. 



1042 



PRACTICAL WIRELESS 



April, 1966 



we audio Ffoetay stereo -33 



A High Fidelity All Transistor 
OUTPUT (per channel) 

10 watts R.M.8. Into 16 

ohm load. 

16 watts R.M.S. Into 3.7.' 

• hm !oa.1. 

TOTAL HARMONIC 

DISTORTION 

.).l% at 5 watts R.M.S. ■» Into 

0.3% at 10 watts > 15 ohm 

R.M.S. 1,000 c.p... J load 

DAMPING FACTOR 20 

FREQUENCY RESPONSE 

tlj dB 20-20, Wlc.p.s. 
HUM AND NOISE-eodB 
CROSS TALK_4adB to -53dB. 
MAINS INPUT SELECTION 

IdO-l 10— 120-200-210-220-240V. 
,0/60 c.p.s. 

SEMICONDUCTORS 
(per channel) 

AC107. OC44(3), OC81ZO. OA5, 

OC127Z, AD149 (2). 

BASS CONTROLS 

1-11 dB to —IB dB at 40 cp.s. 

TREBLE CONTROLS 

+ 16 dB to —15 dB at 10 Ko/s. 

EQUALISATION 

Gram, to std. R.I.A.A. characteristic. 

Tape head to std. C.C.I.R. characteristic. 

SIZE 12Vx4*xM* 
WEIGHT rnib. 
FILTER (Steep Cut) 

7 Kc/s. 11 Kc/s. 15 Kc/S. 



Incorporation of the very latest Milliard Transistors has 
made possible the really outstanding performance ilieures 
of this brilliant design. Compare them with other leading 
makes currently available. 

N'Oi'.:: Ra.e.i output <■- to waits K.M.". (continuous) whioh iboald aot be 
joaluioci W itb I.H.F.M. momentarj anises.) 



Please send 
SAEfor 

leaflet 



Stereo Amplifier providing 10 watts R.M.S. on each channel 

~~ INPUT SENSITIVITIES 

(for 10 watts R.M.3. Into .c 

ohms). 

Pick-up Magnetic 

3.6 m.v. 33'/ L r.p.m. 
7 m.v. 78 r.p.m. 
Pick-up Crystal/Ceramic 40t 

m.v. 
Microphone 5 m.v 
Tape Head 2 m.v. Aux. (Radio 
Tuner. Tape Rec. Ceramic P.O. 
etc.) 100 m.v. (Above sensitivi- 
ties will be doubled when out- 
put load is 3-4 ohms 1 

INPUT SELECTOR 

33'/ r.p.m. 78 r.p.m. Aux. 
Mlc. Tape Head. 

INPUT SOCKETS 

Magnetic P.U.. Crystal/Ceramic 
Pick-up Aux. Tape Head 
Microphone. 

Built to the highett t andardt employ- 
ing latest materials and techniques 

DESIGNED FOR EASE OF FITTING 
IN CABINET OR FOR FREE- 
STANDING USE. 

Tested for satisfactory operation in 
temperatures of up to 50°C. (120°F.) 

EXPORT ENQUIRIES INVITED 

Designed and developed by the 
Audio Fidelity Group of Com- 
ponies. 




h afr^ffl 



THE PRE-AMPLIFIER IS A 
COMPLETELY NEW DESIGN 
IT ELIMINATES THE NECESSITY OF 
MATCHED INPUTS & COMPLICATED 
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ALSO PRODUCES CONDITIONS OF 
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Manufactured and Distributed by LINEAR PRODUCTS LTD. ELECTRON WORKS, ARMLEY, LEEDS. 



THE FINEST RANGE OF TAPE RECORDER 
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TAPE PRE-AMP SSTR/7 

All silicon transistor. Zero hum. High gain and equalise I 
at 74" per sec. to give flat response output. Simple mod. 
described in accompanying instructions allows equalisa- 
tion at all speeds. Suitable for all medium aa lg% 
Impedance heads. Collaro, B.S.R.. etc. /M/h 

ASSEMBLED «•*»/»* 

MINICLASSIC PRE-AMP 
SSPA/49 

Tone controlled high gain preamplifier designed 
specially for application with the SS3/9. All silicon 
transistor. Zero hum. requires 12 volt + H.T. High 
Fidelity complete with tone and volume controls. 
Separate inputs for crystal m g\ i 
oeramio cartridge and. .radio. %}%3 1 m 




ASSEMBLED 

MINICLASSIC SS3/10 

High fidelity 4 watt main amplifier: Ideal for 
use with SSTR/7 and makes complote tape am- 
plifier. 16 c/s to 30 kc/s. Requires 12 volt + H.T. 
and will operate directly from crystal pickup 
6 transistors and two 
diodes all mounted on 
precision printed circuit 
board. Max. music power 
4 watts into «* / 
3 ohm speaker hHf. 
ASSEMBLED ** «*' 



TAPE OSCILLATOR SS013 

Complete unit incorporating push pull transistor oscillator 
giving adequate erase power and recording bias. Ferritepot 
core push-pull oscillator, frequency 50-60 kc. All silicon 
transistor. Provides high voltage (75 v.) D.C. Rail for oper- 
ating record amplifier. High elllciency unit requiring 12 v. 
g%g% I D.C. at 250 mA. The only unit on the market 
hH / - it such an economical price. 

**•*' COMPLETE. 

RECORD AMPLIFIER 

SSH9/3 

Fully transistorised. High voltage H.T. rail de- 
rived from oscillator. Provides substantially con- 
stant current record signal. 1 volt input sensiti- 
vity. Power consumption 1 mA at 12 volts and 
1 mA at 76 volts. Latter derived from 
erase oscillator SS013. 

ASSEMBLED 

Kill mm (i ELECTRONICS m •■■ manufacture 
and supply -^Resistors and capacitors *TV/FM 
Booster Bands 1 and 2. 32/3. * Miniature Trans- 
mitter SS7. 189/6. *30 volt. 3 amp Power Supply. 
69/9. * A range of Silicon 
planar epitaxial transis- 
tors. • Zener Diodes. 

See Practical Electronics 

for further details or write 

to use for descriptive leaflets 

REMEMBER IF IT'S ki;imm o IT'S O.K. 



45/- 



ORDER FROM : To kedoco electronics, beverstone works, TETBURY, glos 

Please supply Address 

Enolose Cheque/P.O. for Postage 2/6 extra lor all orders under £1. 



April, 1966 



PRACTICAL WIRELESS 



1043 



The Amateur Bands— by David Gibson G3JDG 



WANTED! James Bond type agents to sniff 
out the truth. Out of a large mail bag 
this month most letters were about 20 DX? 
No, nor about the VK on topband, or the open- 
ings on 20 either. They referred to "that man" 
NS1A but with a new twist. Apparently we now 
have a NS1B and NS1C too. No, they do not 
count as separate zones for a countries worked 
certificate. Briefly the locations of these stations 
are assured as follows: — On board Radio London; 
10 miles south of Heme Bay; in a motor boat 
with a No. 19 transceiver; on an Irish river (up 
the proverbial creek perchance). Will the real 
NSls please stand up. 

I am taken to task about 80 being deserted by 
George, ZL3QX, who informs that both ZL4IE 
and ZL3FZ have been consistently working EUs 
for some months. Two calls for 80 metre sleuths 
to be on the watch for. The l.f. bands are pro- 
ducing some very good openings at the time of 
writing. Both phone and c.w. are well represented 
— go on, live dangerously, listen now on 160, 80, 
and 40. 



Forty and Down 

Some very fine logs for 160 shows what's about. 
D. Douglas (Dundee), HRO, 60ft. 1-wire, sends 
in what might be confused for twenty, but don't 
be fooled, it is 160, G. Gl, GM, GW, GD, DL1FF, 
DL4SS, EP2IW, HK4EB, JA6AK, KV4CI, 
OE6HS. YV0AA, ZB2A, 9M6BM. R. Iball 
(Worksop), SX28, PR30 pre-selector, 160 raised 
IS1FR, K2DGT, VE2ITU, VE3-AGX, BWY, QU, 
VOIHN, Wl-BB/1, HGT, W2GGL, W8ANO, 
W9YYG, W0VXO. Steve Wilson (Ossett), 
BC348R, 264ft. 1-wire, 160— DJ2GL, DL7FZ, 
GI, GM, GW, GD, HB9-CM, TT, 1S1FR, OK1- 
AEF. AKO. OL5-ADO, AFF. OE1FLW/1, 
OE6HS, PA0DC, PA0PN, VE3BWY, VOl-FB, 
HN, Wl-BB/1, JJU, W8HGW, W0VXO, ZB2AM, 
9H1AE. On 40 Steve's best were AP2LK 
(Pakistan), CN8AW, HK7BCX, VP6BX. On 80 
things are lively too, J. Brown (Llandaff), 19 Set, 
dipole, raised the following on phone, CN8AW, 
CT1-SQ, EE, IT1-AUL, ZGY, MP4BAA (c.w.), 
many VE's, VP-5GC, 7NP, 9AV. W's including 
W8-BON, WNL, YN4CU, ZB2AJ, 4X4BO, 
7X2AH, 9J2MX. Again, on 40, Steve Wilson 
logged CM2WS, COIPY, CR7CI (Mozambique), 
CX2CO (Uraguay), EP2BQ, FG7ND, HK-3AST, 
3UZJ, 4ADD. 4ALE, HV1CN (Vatican), JAIOHV, 
K2-GL, KBT, FCB, K4JC, K0LUZ, KG4AN, 
KP4BBN, LU6FA, PY-1, 2, 3, 5, 6, 7, 8, VP5AR 
(Turks and Caicos Is.), VP9FT, VP7NW, 
W3-MGK, CRQ, W4LVV, WB6JJC/M, YV4CJY, 
ZC4GB, 4X4FA, 5A3TX, 6Y5XG, 9G1FQ, all 
c.w. N. Flatman (Ipswich) R3629, 68ft. 1-wire, 
80 metres bore fruit with CN8AW, HP9ABX, 
K8YWC, UA-1, 3, OX4BK, VE1UW, W-1KVX, 
2CPO, 2ZPO, 3HUM, 4WK, 9CJZ, ZB2-AJ, AM. 
ZL2BE (0830 hrs), while on 40 the same set up 
raised DJ, DL, DM, F, GD, LA, LZ, OZ, 
T4ZUF (?). From further out— JA2BAY, KG4NV, 
VK1ATU. 



Twenty and Up 

More a daytime band but still a hive of activity 
both phone and c.w. as the following SWL's 
report. I. Black (Gillingham), HE30, W6BCX 
Multee antenna, FR7ZC. HI1JMF, KZ5LC, 
MP4BCC, OA4KY, OD5-BV, BZ, EN, PZ1BW, 
UI8AE, VK-2SG, 3LG, 3VJ, 3ALB, 3ATO, 5RT, 
6RU, VP2AA (Antigua), VP5RB, VP6KL.XE3MF, 
ZB2AJ, ZL2-UW, BG, 4X4AS, 5A1TZ, 7Q7PBD, 
7X2MD, 9G1TF, 9J2AB, 9M4TX. C. Claydon 
(Fife), 840c, 60ft. 1-wire, KV4CI, KR6MM 
(Okinawa), CN8MH, C02CO, CR6JA, CR7IZ, 
EA9AQ, LU6FA, OX3LP, UA9KDK, U18ID, 
UM8KAK, VK3-YS, AXK, VK6WT (Perth), 
VQ8BJ, W6-EBG, LVF, VS9ARU, ZD7IM, 
ZD9BE, ZS5UP, ZS6J. From Chepstow one 
"Colin" complete with 888 and 132ft. 1-wire heard 
CR7-BV, CZ, KP4NN. KV4CX SV1CX, 
UA6LP, VK6DR, VS9AWL, ZB4BCA, 

ZC4LK, ZE6JL, ZS6XP, 4X4IK, 9G1FL, 
D. Wraige (Wirral), AR88-LF and 15-20fL 
indoor ant. managed to hear VK.3VS. W6AM and 
W6UED on s.s.b., while Chris Peel (Stoke-on- 
Trent), S750, 90ft. 1-wire around the loft, went 
fishing for DX. Cream of the catch include 
CN8FH, CP8AU, CR6AJ, CX4AW, ET3USA, 
FK8PH, HK7KD, JA2NA, KG6APJ, KR6CH, 
KL7BIC, KZ5AW, LU7FAG, OA4KY, PY1FK, 
PY5AM, TF2WHI, UA9KFS, VE7MS, 
VE1AED/SU, VK-2ADA, GW, 3ADR, UK, 
4SD, 5SM, VP1CY, VP5RB, VU2CK (India), 
VQ8BFA, Wl, 2, 3, 4, 5, 8, 9, 0, W6-1LT, ABC, 
AYM, IPA, W7-SEG, QBA, MKI, XW8AX, 
YA1AW, YA3LCC, YN4CM, YV4IM, ZC4MO, 
ZL-2UW, 3NO, 4BY, ZS6ALM, 5A5TA. 9Q1FS. 
While on 15 metres Chris logged CR4BC, CX1WG, 
EA7GK, ET3USA, HK4XP, JA6QT, HJ8XM, 
OA4KY, OX3JV, PY2DXI, VS9AWR, Ws, 
XW8NZ, 4X4UG, 5A4TI. 5A5PJ, 5N2FEL, 
5Z4AA, 7Q7BN, 9E1VF, 9G1RM, 9H1R, 9K2AD, 
9U5IB, 9Q5QR. F. Simpson (Hull), RX80, 1-wire, 
exact length unspecified, reeled in CR7BL, CN8FT, 
EA8DV, EP3RO, KP4CNC, KW6EJ, KV4CX, 
MP4TBO, OA8V, VE2AFJ. VK.-2NN, 3JA, 4RO, 
9PL, VS9AWR, XW8AZ. ZE1AN, ZS1CZ. 4X4SC, 
7Q7BN, 9H1S, all on 15 metres. On 20 the same 
length of wire heard DU1AA, FK8AC, JA1MJ, 
KA5RC, KR6UL, KW6EJ, KX6DR, PY2BYU, 
PZ1BW, VK3UQ, VP2AA, VS6AJ, YA1AW, 
ZL3AB, 9G1LS, 9L1HX. Reports on 28Mc/s are 
still coming in. C. Clarke (Farnham), 12 valve 
s/het, dipole. G's by the score plus UP2ADZ, 
ZE2JA, ZS9G, mostly a.m. with a few ssb. 
F. Simpson again heard HB9ED, I1CGV, SV1DZ, 
ZE1AN, ZE2JA, ZE3JU. 

Finally a surprise, a genuine log for 144Mc/s, 
our very first. The honours for the christening 
go to David Douglas (Dundee), who says the 
following were "got" with an HRO. (With a con- 
verter, I hope), G3-BRA 80. HUI 200. MCR 200, 
HB0LL, 750, SV1AB 1,200, YU1EXY 750. 
Numbers refer to distance from the transmitting 
stations in miles. 

— continued on page 1051 



, 



BOOKS REVIEWED 






= BASIC ELECTRICITY/ELECTRONICS LABORATORY 

= WORKBOOK. By Training & Retraining Inc. 

E Published by W. Foulsham & Co., Ltd., Slough, Bucks. 

= 224 pages. Size I0j x 8£in. Price 35s. 

THIS is a book whose introduction was printed 
in England and the balance in the U.S.A. 
Doubtless in America this is a useful publica- 
tion but your reviewer doubts its popularity this 
side of the Atlantic. 

It presents a number of projects involving the 
use of a VTVM and /or oscilloscope. Each 
chapter is based on a question and answer 
technique so that the reader is quizzed on know- 
ledge gained as the book proceeds; the answers are 
given later in the chapter. Projects range from a 
simple power supply to a superhet receiver but, as 
one proceeds, various doubts tend to arise. 

Constant irritating references to other volumes 
(by the same publishers perchance) are one source 
of doubt. Another is the number of odd things 
which do not seem to tie up. Page 119 assures 
that we will need a 1.500H resistor, yet the relevant 
circuit on page 122 depicts 1.500kfi. The availa- 
bility of a three-gang 365 + 365 + 162pF also might 
prove difficult. Verdict: Go to America to read 
this one. — DLG. 

= TAPE RECORDING SERVICING MANUAL 

= By H. W. Hellyer. Published by George Newnes Ltd. 

= 336 pages. Size 9| x 7;in. Price 3 gns. 

ON first flicking through the pages of this 
monumental tome the reader is likely to 
register surprised anticipation; on closer 
investigation he might well exclaim : " At last ! " 
For while there have been, and still are. books' on 
tape recorders this one reaches a degree of 
completeness never before achieved. The trouble 
with most books is that excellent though they may 
be in themselves, they try to cover too wide a field 
in the space available. Those interested in the 
servicing aspects often have to make shift with an 
odd chapter or two. Here at last is a book 
devoted exclusively to tape recorder servicing. 

The author, H. W. Hellyer. will need no intro- 
duction to readers of Practical Wireless and 
Practical Television, but it is worth pointing out 
that in producing his magnum opus he was able 
to draw on his own considerable practical work- 
shop experience of the wayward behaviour of tape 
equipment. 

The introductory chapter covers only 14 of the 
total 336 pages but condenses in that space a lot 
of useful information on the basic principles of 
tape recording. The rest of the book is devoted 
to an analysis of tape recorders under 62 different 
trade names! A typical entry details the most 
important aspects of the machine in question — 
specification, special features, dismantling, together 
with notes on special adjustments and servicing 
with pointers to particular faults peculiar to that 
model or range of tape recorders. Much of the 
practical material as mentioned before, is the result 
of personal experience. 



In this way not far short of 300 different tape 
recorders or decks are dealt with. Circuit 
diagrams accompany each model or range with 
mechanical details and component layouts where 
they serve a useful purpose. In so far as a book of 
this kind can ever be complete this one is. 

Your reviewer has only one criticism and that is 
the drawings. They are taken from manufacturers' 
literature and are therefore in almost as many 
styles as there are circuits, which gives the produc- 
tion a somewhat untidy aspect. However, the 
meat is there and no doubt the economy involved 
in not redrawing everything to a standard is 
reflected in the cost of the book. Still, a pity. 

Anyone with any interest at all in tape recording 
from the servicing angle will miss the buy of the 
year if he doesn't order this book. For, taking 
into account the wealth of accumulated data and 
the potential value of the material, it would be 
false economy indeed not to add this work to his 
bookshelf!— WNS. 



= TRANSISTOR RECEIVERS AND AMPLIFIERS. 
= By F. G. Rayer.. Published by Focal Press Ltd. 
= 168 pages. Size 8j x 7iin. Price 30s. 

WITH the increasing cheapness and availa- 
bility of transistors there seems little doubt 
that the number of enthusiasts using them 
will also increase. If you are one of these people 
and you require a not too technical book on the 
subject of receivers and amplifiers then your prob- 
lems are solved for 30s. Commencing with an 
explanation of how these devices work the book 
continues with chapters on aerials and r.f. ampli- 
fiers, mixers, i.f.'s. detectors and a.g.c. Class A. 
Class B. high-power and hi-fi stages. Bonus chap- 
ters include v.h.f. equipment, record players, and 
test equipment and fault findine. A useful book 
indeed, steering a practical middle course between 
high technicalities and boring simplicity. — DLG. 



= MUSICAL INSTRUMENTS AND AUDIO 

= By G. A. B-igps. Published by Wharfedale Wireless 

= Works Ltd.. Idle, Bradford. Yorks. 

P 238 pages. Size 8| x 5*in. Price 32'6d. 

THIS book attempts to interest the concert-goer 
and the audiophile both at the same time. The 
net result is that it falls between two stools, and 
at 32s. 6d. it is questionable whether it is worth 
bending down to pick it up. It discusses instru- 
ments of all classes, their manufacture, the sounds 
they emit, wave forms, the formants, harmonics and 
just about everything. It is degraded by frequent 
attempts by the author to be funny, and this is 
further aggravated by the numerous unfunny 
cartoons and sketches from old issues of Punch. 
There are special chapters written by experts in 
their field, and had the general style of the book 
followed the examples set by these writers then the 
improvement would have been such as to justify a 
firm reccommendation, as it is, however, your 
reviewer remains unimpressed. — DLG. 



April, 1966 



PRACTICAL' WIRELESS 



1045 






Don't Miss Next Month's Big Value Issue! 



FREE GIFTS 




RESISTOR COLOUR ► 
CODE CALCULATOR 

A simple-to-use aid for the constructor. 
Just set the colours and the correst resis- 
tance value is shown in the "window". 
Resistor tolerance is also indicated. 



24-PAGE BOOKLET GUIDE 

TO VALVE CIRCUITS 

First of 3 month-by-month FREE Booklets covering 
at-a-glance data on r.f., i.f. and a.f. amplifiers, fre- 
quency changers, oscillators and many other aspects 
of radio and electronic equipment. 



Other Outstanding Features: 

1. The 208 Bandspread Receiver. 

2. Simplified Cabinet Design. 

3. Comprehensive ATU. 





ORDER NOW! 



MAY ISSUE 

ON SALE A /£ 
APRIL 7th ^/ O 



SEE FORM ON PAGE 1046 



1046 



PRACTICAL WIRELESS 



April, 1966 




WIRELESS 



_ — 



FREE INSIDE 



RESISTOR COLOUR 
CODE CALCULATOR 
24-PAGE BOOKLET 

GUIDETO VALVE CIRCUITS 




THE 208 

BANDSPREAD PORTABLE 



from 

next month 

PRACTICAL 

WIRELESS 

will be 

published 

in a NEW 

LARGE-SIZE 

FORMAT 




From next month's issue, on sale April 7, PRACTICAL WIRELESS will appear in an 
attractive new format, with an increased page-size and heavier quality paper. Many special 
features plus more FREE insets, have been planned ahead for the new large size issues. 
See overleaf for details of a FREE Resistor Calculator and a FREE 24-Page Booklet on 
Valve Circuits inside every copy, next month. 



INCREASED 
DEMAND 

Make sure of 
your copy - hand 
this form to 
your newsagent 
today ! 



To 

(Name of Newsagent) 

Please reserve/deliver the May issue of PRACTICAL WIRELESS (2'6), on sale April 7, and continue 
until further notice. 



NAME 

ADDRESS 



A 

m 



v 



EL 
KEY 

ELECTRONIC 
MORSE KEY 

P. MURPHY 




THTS device was built, taking into account the 
large variety of types of morse one meets with 
in the communications world. Whether it be 
slow or fast characteristic or otherwise, e.g. slow 
dashes — fast dots, or fast dashes — slow dots, short 
" space " or long " space ", and not forgetting of 
course perfect well balanced morse. The key was 
thus designed to be as versatile as possible to take 
into account the above mentioned types of morse, 
while retaining the advantage of being an auto- 
matic device, and works over a range varying from 
a very very slow pace up to about 40 w.p.m. The 
key is therefore suitable for both amateur and pro- 
fessional and would be a very useful asset in train- 
ing establishments. The key is inexpensive to make, 
suitable for the home constructor to build and has 
the advantage of being portable. It is economical 
to run and uses standard transistor batteries. 



Dash contact 



Centre handle or Paddle" 

which Is operated by hand 

from side to side to maKe 

contact with the dash 

or dot contacts thus 

producing dashes and dots 

as required 



Dot contact 



Relay contacts (1) 
Closed in non-operated £ 
position 




To transmitter 



R1 
200fl RLC 2' 

Relay contacts (2) Open in 
non-operated position 



Fig. I s Circuit diagram of transistorised key. 



The newcomer to the electronic key may at first 
think it is difficult to use, but like everything else 
a little practice each day for a week or so will soon 
convince him that it is not as difficult as it first 
seemed. 

Construction 

Handle or Paddle: — The construction of the 
handle can present a small problem, as it must be 
capable of moving from side to side and returning 
to its neutral or " central " position automatically 
when the finger pressure is released from it, also 
the gap between its central position and the dot or 
dash stud into which it comes into contact must be 
very small indeed, approximately between tV and 
sVin., and a general rule which can apply here is 
that it is better to have too small than too large a 
gap- 

The paddle described, if con- 
structed properly, can give excel- 
lent results and is both simple 
and easy to construct. However 
the would-be constructor should 
pay particular attention to the 
paddle, a bad handle can spoil 
the performance considerably, 
e.g. the letter C is sent thus: 

• a handle which has, 

for example, a large gap can give 
an effect which could sound like 
— • — which produces the letter 
N twice, an experienced elec- 
tronic key operator can, of 
course, overcome things like this, 
but for the beginner a good 
paddle is most essential. See 
Fig. 3. 

The paddle consists of a nail 
file (5in. long), a piece of wood 
34in. x Hin. x Jin. upon which 
the nail file is mounted, and an 
L shaped piece of metal 1 1 /5in. 
long and Jin. wide in the horizon- 
tal and 1 1 /5in. x fin. in the ver- 
tical plane (See Fig. 3) which is 
used to support the nail file on 
the wooden base. The L shaped 
piece is secured to the nail file by 
small nuts and bolts. 



To AE oscillator"*" 
( optional ) 



RLC 3' 
Relay contacts 3 Open in 
non-operated position 



1048 



PRACTICAL WIRELESS 



April, 1966 



Paddle 



ToTX, 



:r2 

■39kfl 




RLC 3 open when key is in 
non-operated position 



■ RLC 2 open when key is in 
non-operated position 



C4 C3 

0-02^F C"02jjF 

41-Hr- 



C2 

0'02jjF 



Output 



R3< R5<£ R6< R7- 

4-7kn> 6«8kn> 6-8kn> 6-8kn: 



1000 c/s phase shift, 
audio oscillator 



fig. 2: Diagram of electronic key and phase-shift audio oscillator. 



Two flat pieces of formica can be glued to each 
side of the nail file near its end, which tends to 
make the paddle easier to operate. 

The wooden base can be either glued or screwed 
to the chassis. 



Function of Components in Fig. I 

The components, VR1, Rl, CI, make up the 
time constant (CR) for the space (time interval) 
between consecutive dots or dashes. Increasing VR1 
will therefore increase the space, or vice-versa, the 
max. space limit chosen was the max. practical 
limit that would be required although spaces up 
to unity can be obtained with this type of transis- 
tor. They are not required in this case. The min. 
space depends approximately on the value of CI. 
In the circuit (Fig. 1) extreme max. and min. values 
should be obtained, and here as well as the other 



Bolts 




Fig. 3i Complete "paddle" for the key. 



variables in the circuit, the constructor may, if he 
so desires, choose closer limits by using the appro- 
priate value of VRI, which he can quickly deter- 
mine by experiment. The mark length is slightly 
affected when varying the space control VRI. 

Rl Under no circumstances must this 200CI 
resistor be omitted or reduced in value as it 
is a limiting resistor and 200£l was found to 
be the min. critical value. 
The components, VR2, R2, C2, make up the 
time constant for the dash side of the circuit. C2 
and R2 by themselves provide for the shortest 
length of dash and by increasing VR2 the length of 
dash can be increased, here again max. and min. 
values have been chosen, and it is up to the con- 
structor if he wishes to modify these. 

The components, VR4, R3, C3, make up the 
time constant (CR) for determining the length of 
dot and as in the case of the dashes extreme max. 
and min. values were again 
chosen, R3 and C3 together 
decide the shortest length of dot 
and VR4 can be increased to 
lengthen it. 

VR3 varies the overall speed, 
the ratio of dot to dash and 
space etc., are fixed by VRI, VR2 
and VR4, and VR3 varies the 
speed of the cycle as a whole, 
though slight variations do occur 
in the ratios especially at higher 
and lower speeds. However this is 
easily overcome by setting the 
ratios at approximately the speed 
one is going to work at and 
adjusting as necessary. In any 
case only one control will need 
adjusting. Increasing VR3 de- 
creases the speed and vice 
versa. 



Piece of L shaped 
metal 



Nail file 



April, 1966 



THERMOSTATS 

Type *A' 15 amp lor controlling room beaters, 
greenhouse. airing cupboard. Has tpindlc for 
pointer knoh quickly adjustable from 30" — 
80' P. 9/6 [ilus l/. pout. Suitable box for wall 
mounting. 5/-, p. a P. 1/-. 
Type 'B' IS amp. This Ib a 17ln. long rod 
type made by the famous Sunvlc Co. Spindle 
adjusts this from 50-550°F. Internal *crew 
alters the setting «o this could lie adjustable 
over 30 to 1.000°F. Hultohlc for controlling 
furnace, oven. kiln. Immersion heater or to 
make flamestat or ore alarm. 8/6 plus 2/9 
post a n d insurance. 

Type 'C Is a small porcelain thermostat as 
fitted to electric blanket*, etc. 1, amp. 
setting adjustable by sere'" through side.. 3/6. 
P. * P. fid. 

Type 'D' We call this the Ice-stat as It cuts 
in and out at around freezing point 2/3 amps. 
Has many uses, one of which would be to 
keep the loft pipes from freezing if a length 
of Mr blanket wire (16 vd". 10/-) Is wound 
round the pipes. 7/8. P. * P. 1/1. 
Type 'E 1 This 1» a standard refrigerator 
thermo-tai. Spindle adjustment* cover nor- 
mal refrigerator temperature. 7/6 plus 1/- P. 

TRANSISTOR BARGAIN 




fabric — 

looks very 
smart— suit- 
able for receiver— amplifier — extension 
Speaker etc — Originally listed at 29/6— 
but offered this month at only 16/- plus 67- 
post and insurance also given free with it is a 
printed circuit board to suit it and building 
instructions for fine two wave radios — Don't 
miss this grand offer. 

|"TAPE RECORDER BARGAINSH 
Capstan Driven, 5 Transistors 

SPECIFICATION: — 200/7000 C.P.S.— 
400 MW ootpnt— double track-twin 
speed (3} and 7!) fast rewind time—, "nn. 
sdooI gives one hour playing with 
standard tape weight 7 lbs. Sue 8 x U x 
5«. Complete with batteries, micro- 
phone—tape spool and instruction 
manual. Nothing to go wrong if you use 
a good tape and keep beads clean. 
Demonstration gladly given at our 
Croydon shop. 

Special Snip Price This Month, fll.11.0. 
Post and Insurance A/6. 

THE 'MINY' 

Beat of the spool driven machines, 
remote control on iqlko, battery opera- 
ted. 

£6.19.6 plus 5/- post 4 Inf. 



TRANSISTOR 
SET CASE 

Very modern cream 
cabinet, size SJ x 
3 x 1,'in. with 
chrome handle, 
tuning knob and 
scale. Price 4/6 Plus 
2/- postage. 



GANGED POTS 

Standard type and size with 
good length of spindle — 
mady by Morganlte. List- 
price is in/- each but if vou 
act quickly yon can have 
them ai 12/- do*, 'or 1/6 each if less than doz). 
Following values In «tock all ' lln" — 5K •* 
5K— 10K*10K— 100K . 100K— 300K-500 
K all new and unused. Post 2/9 on 1st doz 
then 1/- i»ci doz. 6 doz or more post free. 



FINE 
TUNERS 

00 pF with long spindle 
:.9 Illustrated. 1/6 or 12/. 
clo.-. Twin 50pF not 
lotin spindle. 2/6 a 2«f- doz. 






PRACTICAL WIRELESS 

See in the Dark 
INFRA-RED BINOCULARS 

These if fed from a high 
voltage source will enable 
objects to be seen iti the 
dark, providing the ob- 
jects are in the rays of an 
Infra-red beam. Each eye 
tune contains a complete 
optical Ions system as well 
as the infra-red cell. These 
optical systems can be 
used as lens for TV camera— light cell otc. (details supplied). The 
binoculars form part of the army night driving (Tabby) equipment. 
They are unused and relieved to be to good working ordei, but sold 
without a guarantee. Price £2.17.6 plus 10/- carriage and insurance. 
Handbook 2/8. 

AMPLIFIER BARGAIN— NOT BEATABLE 
750 mW 
TRANSISTOR 
AMPLIFIER 

4 tranabtnr* idcIlhHdp two 
to push-pull .opm for crystal 
or magnetic microphone or 
pick-up — feed back loops — 
•eDtltlvlty m v. 

Price 19/6 

Post and insurance 2/6. 

M ohm Speak* 12/6 jxtw. 

, STUPENDOUS OFFER £11 for 

be Princess superbei 
eseribed below 




iif.ie ' 



lha 




has been most 

Inlly designed lor high 

performance. Only 

recently (under 

another name 01 

course) this was on 

offer is many radio 

shops, for £10.19.6, 

but we have been 

fortunate '" obtaining 

the parts at a verv low 

price and now pass 

thM saving on u> you. 

If you act quickly yon 

can purchase this for 

only 39/6 plus 3;6 post and insurance. Note these features. 

• Long and Medium Wave 

• Long clear dial with travelling pointer and slow motion drive 

• Push pull output approximately 350 in.w. 

• A.\ C. and feed back 

• Dust cored H.Q. l.F. transformers 

• High selectivity (.Trite aerial 

• Six tested and guaranteed transistors 

• Printed circuit board lor fool proof assembly 

• Economy output circuit gives long life from P.P.3 battery 

• Permanent magnet moving coll speaker 

• Cabinet size jfinir. Carrying strap 

You get over SO parts (list value over £10). In fact everything 
vou need and easy to follow wiring and aligning instructions. 
Don't miss this wonderful offer. Make up several while you have 
the chance. Use them as present* ami vou'll be loved for ever. 
Battery 1/9 extra. Data separated 2/H. 



1049 

FLUORESCENT 
CONTROL KITS 

Onr 90 watt kit for 5 - fluorescent tube Is the 
best money can buy it contains latest slim 
line (eas\ to hide awayi choke made by one 
England's largest companies — starter — 
tube ends — two chrome clips. All wired up 
ready — fit it in a jiffy with mat » lew screws — 
and it's guaranteed for three years— price 
only 25/- complete plus »/6 post and Ins., 
or complete as listed hut not wired up 22/8 
plus 3/6. 

Other sizes: 
2' 20 watt wired 22/6 not wired 19/8 + 3/- 
2' 40 watt wired 25/- not wired 22/6 -» 3/6 
S* 40 watt wired 19/6 not wired 17/8 + 3/- 
4' 40 watt wired 19/6 not wired 17/6 + 31- 



PLANT RAISING 
Be first 
this year 

Boll heating 
transforn 







INFRA-RED 
HEATER 

Make np one of these latest typo 
heaters. Ideal for bathioom, 
kitchen, bedroom, etc. They are simple 
to make from uur easy to follow in- 
structions — use silica enclosed elements designed foi the correct infra- 
red wavelength (3 microns). Price for 780 watt element and metal- 
casing as illustrated, 21/6 plus 3/fl post and insurance. Pull switch 
3/- extra. 

THIS MONTH'S SNIP 




Where postage Is not definitely stated as 
as an extra then orders over £3 arc post 
free. Below £3 add 2/9. 



Garrard 1000 
Record Changer 

One of the latest record 
changers that this famous 
company make — Automatic 
selection of records which 
ma* be mixed — may also 
De played manually. 
Finger tip adjustment 
of stylus pressure. 
Fitted with monobea-J 
but pick-up wired lor 
stereo — suitable 200/230 — 
A.C mains. Cabinet space 
required 141 x 12,in. with 
4Jin. above and 2Jin. below. DON'T MI8S THIS SPECIAL 
SNIP only £5.5.0 (post and Insurance 6/6). 




Bargain for Experimenters and Constructors 

Printed circuit outfit with 16 page booklet of circuits and projects 
case and dials, laminated copper clad board niching fluid etc. etc. 
all for 7/6 plus 1- post. 





rlrc and 
Suitable 
standard &ize 
garden frame. 12/6 
plus 2/6 post & in*. 



l. SOUND 

POWERED 
=TELEPHONES 

I'hi be FNttifl iiu lot- 
teries: in luct they 
have only to be con- 
nected by a pair of 
wires. They can thus 
be fitted Into existing 
bell circuits. Result* 
are extremely good 
and maintenance 
costs are nothing. 
Handsets only 15/- 
each. Post, etc. 3/6. Two. post free. 



Speaker Bargain 



h f I ii x 
Bsugiel t\ ps 
tatewhethet 

3 ohm or is 

ohm speiHib 

coil. Will 

handle upto 10 watts. Brand new by famous 

maker. Price 29/8 + 3/6 post and Insurance 

Waterproof Heater Wire 

16 yds. length 70 watts, self regulathkt 
temperature control. 10/- post tree- 

FOUR- 
STATION 
INTER- 
COM 

Will save time and 
improve efficiency- 
Ideal in home — office— shop— surgery, etc. 
Complete outfit comprises Master unit and 
three sub-Utlons each of which can call 
the inast-y and have full two-way working. 
So wlnrg problems as subs fitted with. 
SOft tM , flex and they plug into sockets. 
Also Included Is packet of staples — and 
battery. Nothing else to buy— *7.16.0 plus 
4/6 post and insurance. 

ARMCHAIR CONTROL UNIT 

Remote Controller— 
lor Philips, Stella and 
Coaaor T.V. set* out 
adaptable to most 
ithers. and to model 
control. Comprises 3 
rocker switches, two 
variable resistance* 
1 and componenta b> 
, eluding Mullard OA81 
\ — Knobs — 10 way 
ping— lift. 7 way 
cable etc. etc 
Lis! price (8,3.0 yours 
lor only 12/6 plus 2/- 
pc*i and insurance. 





ELECTRONICS (CROYDON) LTD 

Post orders to: Dept. P.W., 4 Springfield Road, Eastbourne, Sussex 

Callers: 266 LONDON ROAD, WEST CROYDON, SURREY 

NEW BRANCH FOR CALLERS: 1 02 TAM WORTH Rd., CROYDON (op. W. CroydonStn.) 



1050 



PRACTICAL WIRELESS 



April, 1966 













Mon. — Sat. 9 a.m. 


D 


C 1 


r IfAllfC MA II Al 


incD 


PA 


All valves — 5.45 p.m. 


i\ 


•do 


1 • VALVE MAIL III 


iUtn 


uu> 


brand new No Early Closing 










and boxed Open Daily to Callers 


21 la 


STREATHAM ROAD, MITCHAM, SURREY 




Tel. MITcham 6202 


OA2 


6/3 


«BK7 


10/6 61,1 9/6 


10LD11 10/- 30C1S 9/6 


AXF4 


1/9 


BB91 


3/- 


El-OS 


10(- - NTS 15/- rvs.'i 6/- 


UCL83 8/9 


oca 


6/- 
7/9 


BBB8 


7/6 


6L6G 7/- 


10P13 12/6 


30C17 12/- 


ATI'S 


7/- 


KH(.'33 


6/- 


EF1S3 


6/6 


N108 15/- 


PYR0O 5/8 


UF41 7/- 


1A7 


6BS7 


15/- 


6L18 7/6 


12AII8 20/- 


S0F5 9/- 
30FL1 10/6 


ATP7 


4/8 


B BC4 1 


6/6 


EF1.S4 


6/6 


XGT1 8/- 


PY801 6/3 


UF89 6/- 


IDS 


6/- 


6BW6 


8/6 


6Q7G 5/6 


12AT6 4/6 


AU2 


80/- 


EBC90 


3/6 


B&32 


3/- 


XGT7 25/- 


K2 4/- 


U1.41 6/9 


IBS 


7/8 


8BW7 


8/6 


6Q7GT 9/- 


12AT7 3/3 


30L1B 12/- 


AU5 


6/- 


F.BF80 


5/- 


ELS3 


17/6 


OZ4 41- 


K19 71- 


UL84 5/6 


1LDB 


5/- 


6C4 


1/9 


6SA7 7/- 


12AU6 5/9 


30L17 12/6 


AZ1 


8/9 


BBF88 


7/3 


EE34 


9/6 


PCS6 10/- 


RGS/500 


UM80 71- 


1N6GT 


8/- 


6C5G 


4/- 


68C7 6/6 


12AU7 5/- 


30P12 10/- 


AZS1 


7/9 


K. •!!•',>» 


5/9 


EI.41 


7/3 


PC88 9/3 


69/- 


ULIi 13/6 


IBS 


6/- 


8C6 


8/9 6SG7 41- 


12AX7 4/6 


30P19 14/- 


CBL31 


28/6 


EBU 


17/6 


EL42 


7/6 


PC97 71- 


8130 10/- 


UU7 10/6 


184 


6/- 


6C8G 


6/- 


6SH7 2/6 


12BA6 81- 


30PL1 11/- 


okjw 


5/- 


EBL21 


10/6 


ELS4 


4/6 


PCC84 5/8 


8P4 9/- 


L'Ufl 8/- 


IBS 


8/3 


6CD8G 22/B 


6SJ7 5/- 


12BE 4/9 


30FL13 12/6 


CL33 


12/8 


EBI.31 


27/6 


EL90 


6/- 


PCC89 8/8 


-SP41 1/6 


UY21 7/6 


1T4 


2/6 


6CH6 


8/- 


68K7GT 4/9 


12BH7 5/9 


30PI.14 18/6 


CYS1 


10/- 


ECC'fll 


3/3 


EL95 


8/- 


PCC189 10/- 


8P61 1/- 


VY'41 4/6 


8A4 


8/6 


60W4 


14/- 


63L7GT 4/9 


12C8GT 7/6 


35A5 17/- 


DAC-32 


7/8 


BOOS9 


5/- 


KM 34 


9/- 


PCFSO 6/6 


8C25 19/6 


UY86 4/9 


804 


6/6 


6D8 


2/9 


68N7GT 41- 


12E1 19/8 


35 L6 6/9 


1 ) A l''J 1 


3/3 


ECC83 


4/6 


i:\ BO 


6/- 


PCFS2 6/- 


SL'2150 18/6 


VCR97 27/8 


3Q5 


8/6 


6E5 


5/9 


68Q7 6/- 


12JSGT 2/3 


35 W4 4/9 


DAFSS 


6/- 


BOC84 


5/6 


EM81 


7/- 


PCF84 8/- 


T41 9/- 


VCKS17B 


334 


4/9 


6F1 


9/- 


6C4GT 10/- 


12J7GT 7/8 1 35Z3 10/- 


IK.C'.lli 


8/- 


BO 58 


5/9 


EM84 


6/- 


PCF86 8/6 


TDD4 71- 


30/- 


3V4 


6/- 


6F5G 


5/- 


6U5G 7/6 


12K7GT 8/- 1 35Z4GT 3/9 


DF33 


8/- 


ECC88 


8/9 


Esri5027/6 


PCF801 9/9 


T1J41 20/- 


VCRS17C 


6R4G 


8/- 


6F8G 


4/- 


6V6M 8/- 


12KSGT 8/8 


35Z5 5/8 


DF70) 


6/- 


ECK80 


6/6 


EY51 


6/- 


PCF802 9/9 


L"10 7/- 


80/- 


5U4G 


4/- 


6F8G 


4/6 


6V6G 6/6 


12Q7GT 81- 


87 5/- 


DF91 


2/6 


BCF83 


6/- 


EY86 


6/3 


PCF80310/6 


l."14 71- 


VMP4G 17/- 


SV4G 


8/- 


6F11 


12/6 


6V6GT 71- 


12SA7 6/6 


42 4/8 


DFD2 


2/8 


F.CH-J1 


19/- 


EZ35 


4/9 


PCF806 12/- Ll'J 80/- 


VP4B 12/8 


6TSGT 


4/8 


6F13 


6/- 


6X4 8/6 


128G7 8/6 


SOBS 8/8 


DFD6 


28/- 


BOH3S 


18/- 


EZ40 


5/6 


PCF808 12/6 | l"2S 10/- 


VU105.'3O5/- 


6Z4GT 


8/- 


6F14 


12/6 


6X5G 4/9 


12SH7 2/9 


50C5 6/8 


DH77 


8/6 


BCB42 


8/- 


F.Z41 


6/- 


PCL83 6/6 I" 26 10/- 
PCL83 8/- 078 8/8 


VRI50/305/- 


6/30L2 


10/- 


OH 


9/6 


8X5GT 7/6 


12SJ7 3/9 


50CU6G24/9 


1 ■ K .-:■.- 


7/9 


ECH81 


5/6 


EZ80 


5/6 


VT9J 29/- 


6A7 


15/- 


6G6 


2/6 


7B6 11/- 


129K7 8/9 


B0L6GT 6/- 


DK91 


5/- 


BOHSa 


6/6 


EZ81 


3/6 


PCX84 7/- 1191 11/- 


VT31 69/- 


6A8G 


12/6 


6H8 


1/3 


7B7 7/- 


12SR7 5/- 


75 5/- 


DK92 


7/9 


Ei.-l.--n 


6/- GZ30 


S/6 


PCLB8 7/3 , 1 251 11/6 


VL111 6/- 


6AC7 


3/- 
4/6 


6JSM 


6/8 


7C5 10/- 


1287 20/- 


78 4/6 


DK90 


6/6 


EOL82 


6/6 


GZ32 


9/- 


PCL36 8/9 O901 12/- 


vri-.'o 8/- 


6AK5 


6J5G 


2/6 


7C6 8/- 


19AQS 7/6 


80 5/- 


OL7n 


7/- 


ECUS 


9/- 


GZ84 


9/9 


PEXA4 20/- I" 403 8/6 


•■ 1 X - 85?- 


6AL5 


8/- 


6JS0T 


4/6 


7D5 8/- 


20D1 10/- 


SSAG 8/6 


DL82 


4/9 


BOL88 


8/6 


KT38 


22/B 


PEXB4 20/- ' C80I 18/6 


WSIM 5/- 


BAMS 


8/6 


6J6 


8/- 7H7 5/- 


20F2 11/- 


150B2 14/6 


DI.93 


3/6 


EF9 


20/- 


KT61 


17/6 


r EN 4.i 6/- 


l ABI.'SO 5/8 


X 78 26/6 


6AM6 


2/9 


6J7M 


8/6 


7R7 12/- 


20L1 15/- 


150C4 12/6 


I • f -'-■ 1 


6/- 


F.F36 


3/- 


KT66 


20/- 


PEX46 2/9 


1. 'AF42 71- 


X79 41/- 


6AQ5 


6/- 


6J7G 


4/3 


7S7 18/6 


20P4 14/- 


801 5/- 


DL95 


6/6 


KF37A 


9/6 


KT81 


10/- 


P1.36 9/6 


UBl'Ml 6/6 


XH1-5 51- 


6AS7 


£2/6 


8.I7GT 


8/6 


7Y4 5/- 


20P5 12/- 


807 7/9 


DM0 


6/- 


EF39 


5/- 


KT88 


28/- 


PLS1 7/- 


EBC81 71- 


Xl'l-S 5/- 


6AT6 


8/6 8K6GT 


5/- 


9BW6 81- 


25A6 6/6 


813 80/- 


DM70 


5/- 


El- 11 


6/6 


KTW61 4/3 


PL82 6/- 


l lil'80 5/9 


X 91.11-5 10/- 


6AU6 


6/- 


6K7M 


5/- 


10C1 12/6 


25L6GX 4/8 


866 10/- 


DY86 


7/- 


EFS0 


21- 


KTZ41 


8/- 


PT-83 81- 


UBF89 8/3 


Y63 7/6 


6B8G 


2- 
4/9 


6K7G 


1/3 


10C2 12/- 


23Y5 6/- 


9B4 41- 


DY87 


7/9 


EF80 


4/6 


ML4 


17/6 


P1.S4 6/3 


UOCSi 8/6 


3EG1 40/- 


6BAS 


RK7GT 


4/6 


10F1 12/6 


25Z4 6/3 


1825 61- 


K.-.-oo 


14/- 


EF85 


4/6 


MI.fi 


12/6 


PL500 14/6 


i;CC80 8/6 


3FP7 12/6 


6BF.6 


4/9 


6K8M 


8/6 


10F3 12/- 


25Z5 7/- 


4022AK 15/- 


EAB0 


2/- 


EF86 


0/6 


MBP4 


12/6 


PX4 18/8 


rcl-Hil 8/6 


6CP1 30/- 


6BH6 


71- 
7/8 


GK8G 


3/- 


10F9 9/9 


23Z6 8/6 


6763 10/6 


EABC80 5/6 


BF89 


4/- 


Ml! 14 


4/- 


PYB3 8/6 


DOH49 7/- 


CV1526 40/- 


6BJ6 


6K8GT 


3/3 


10F18 9/- 


28D7 5/- 


7193 1/8 


EAF42 


7/6 


EI'Ol 


2/9 


MX 40 


12/6 


PY81 5/6 


UCH81 8/3 


ACR13 


6BQ7A 


7/6 


8K25 


20/- 


10L1 10/- 


30C1 6/6 


7475 2/6 


K I'- 1 1 


4/U 


BFM 


2/6 


K37 


10/- FT88 5/H WiUt* 7/0 


£3.0.0 












SETS OF VALVES 




SPECIAL 24 HOUR SERVICE S fecial 24 Hour DAF91. DP91. DK91. DL92. DL94 .. .. get of 4. 19/- 

nnrnirrcTviiK a cocrui rrv ■»!»«• DAF96. DF96. DK96. DL96 Set of 4, 25/- 

OBSOLETE TYPES A SPECIALITY c-*.— .. M„;l BRAND NEW TRANSISTORS 


QUOTAT 


"*" OC35 


9/6 


OC72 6/- ' ICWI 6/- 


Postax 


• 6d. per Valve. c.w.o. No C.O.D. Order Service 


4/6 
3/6 


OC81 4/- OC82D 6/- 
OC8lm/pr 12/6 OC170 7/6 




Send S.A.E, for list 


OC71 


4/6 


OC81D 4/- OC200 8/- 




Super 8/RS/DD 

Frequency range 40 c/s— 20,000 c/s 

Impedance 10/15 ohms 

Power handling capacity 6 watts 

(12 watts peak) £7 (tax paid) 

Super 10/RS/DD 

Frequency range 30 c/s— 20,000 c/s 

Impedance 10/15 ohms 

Power handling capacity 10 watts 

(20 watts peak) £11 13 4 (tax paid) 

Super 12/RS/DD 

Frequency range 25 c/s— 20,000 c/s 

Impedance 12/15 ohms 

Power handling capacity 20 watts 

(40 watts peak) £17 10 (no tax) 



POST THIS COUPON TODAY 

For fully illustrated 8 page 
booklet on Wharfedale 
Speaker Units fDept. pw.4) 



These speakers 

from the Wharfedale 

Super Range are fitted with roll 

Surrounds for low resonance and double 

diaphragm assemblies for extended H.F. response. 

RANK WHARFEDALE LIMITED Idle, Bradford, Yorkshire 
Telephone Bradford 612552/3 Telegrams 'WharWel' Bradford 



NAME- 



ADDRESS., 



TOWN.,..,. , ....COUNTY - .. 



April, 1966 



PRACTICAL WIRELESS 



1051 



Transistors 

These are GEC S3 type transistors. Type GEC 
SI will perform equally well and although others 
have not been tried in Fig. 1, it is presumed that 
any p-n-p type transistor which is suitable for a 
class B output stage e.g. Mullard OC72 would be 
suitable, GEC types were chosen because they 
were less expensive at the time. It may be 
necessary to adjust some of the component values, 
if other types of transistors are used, because 
differences in performance was noticed, even with 
individual transistors of the same type, but these 
variations were slight. 

Layout and General Information 

For the right-handed operator it is necessary that 
all the adjustable controls can be easily turned with 
the left hand, so that adjustments can be made 
whilst actually operating, and saves the necessity of 
having to stop to alter the ratios or speed etc. A 
left hand operator should have access to the 
variable controls with his right hand. 

The two pairs of wires from the relay contacts 
R1.C2. RLC3 should each preferably be terminated 
in a plug and socket at the back of the box or 
chassis to prevent wires going to the tx and osc. 
(only for separate osc. not built in the key as in 
Fig. 1) from getting in the way near the paddle. The 
on /off switch would naturally be convenient in the 
front, (when Fig. 2 is built only one pair of con- 
tacts need be terminated in plug and socket for tx). 
The max. height of the handle above the bottom of 
the box or chassis should not exceed 2in., this 
heieht also includes the width of the nail file. 

When operating the key the correct position of 
the arm and hand is absolutely essential and it is as 
follows: — The arm from the elbow down should 
lie relaxed on the table, with the thumb side of 
the hand upwards, the handle of the key is .then 
operated with thumb and first finger in a gentle 
side to side movement. The whole of the hand up 
to 'he wrist should follow the movement of the 
fingers and in this way. an onerator can send for 
hour after hour without getting tired. The writer 
knows of no other method which can eaual that 
just described for operating the key and getting 



the best results from it with the minimum of effort. 

When assembling the device, especially when 
experimenting with it, it was found on several 
occasions that minute pieces of solder, dust, etc., 
got between the relay armature and pole face pre- 
venting the key from functioning, and it was only 
after testing everything else that the relay was 
examined and the fault discovered, however, a 
thorough clean-up after the unit is placed in the box 
would avoid this fault altogether, together with 
careful soldering. 

When Fig. 2 is built (i.e. key and oscillator 
together) a loudspeaker may be built-in or a " split 
phones " arrangement with a 3-way switch, i.e., e.g. 

Switch Position 

1. One earpiece to Radio Reciever, 
other earpiece to audio oscillator. 

2. Both earpieces to Radio Receiver. 
3.. Both earpieces to oscillator. 

While on the subject of Fig. 2, the current con- 
sumption with oscillator and key drawing from the 
batteries, varies between some 20 to 30mA. neg- 
ligible current is drawn when not keying; however 
the on /off switch from the supply should be 
switched off when the key is not in use. 

The photograph shows the key when built; it 
can however be enclosed in a much smaller space, 
and must not be too light in weight although the 
batteries do help to make up weight, also the width 
should not be less than say 3 to 4in. This helps to 
stabilise the unit and prevent it from moving when 
keying. Component tag boards were screwed to the 
•side of the box and the opposite side was used for 
the variable pots. A suitable lid fits on top and the 
workings are then completely enclosed. 

Although there are many different combinations 
of capacity and resistance which would give the 
same results as the key in Fig. 1 the circuit design 
is a standard, and providing the constructor can 
comply with the transistor limitations, and provide 
enough current to operate the relay, a wide range 
of combinations are open to him. Dots are nor- 
mallv to the riiHt operated by the ♦humb. dashes 
are normallv to the left onera'ed by the first finger. 
In Fig. 1 both dots and dashes can be obtained 
from either side, should an operator require the 
opposite. 



ON THE SHORT WAVES 

— continued from page IC43 

There are VK's on topband and at least one of 
our reporters has heard a JA. Anyone else hear 
these remote parts at this frequency? For those 
wanting to know when to listen on 20 and 15 the 
answer is that they are open from 0600-1800 n.M.T, 
Someone will doubtless hear a piece of fabulous 
DX at 1081 now that I've said tha*! Listen on n'-one 
only for VQ8AZ and VQ8BZ in Mauritius. ZD8's 
are plannine some DX-peditions in the Caribbean 
area soon, ZD5M is loose on 21 c.w. (Swaziland), 
while on 20 c.w. TL8SW is quite a rare bird. 
ZS2MI reported active from Marion Island, and 
spies report that an expedition is promised for Rio 
de Oro soon. Contests for March include 12-1 3th, 
ARRL DX Contest (phone); 19-20th. BERU: 26- 
27th, ARRL DX Contest (c.w.); April 3rd. Low 
Power (QRP) Contest. All logs welcome, deadline 
for May issue is March 27th. 



PRACTICAL ELECTRONICS 

APRIL 



4 ELECTRONIC AIDS FOR THE HOME 

FREE CAPACITANCE AND 

RESISTANCE CALCULATOR 

MORE "BONANZA BOARD" PROJECTS 

GUITAR SOUND EFFECTS UNIT 
AUDIO POWER BOOSTER 



On sale MARCH 17- 



-2s. 6d. 



A COMMENTARY BY HENRY 

PRACTICALLY 

WIRELESS 



No. 20 
M.T.B.F. 



r THE perennial subjeot of break- 
down has haunted the elec- 
tronics industry from the "shed- 
in-the-back-garden " days to this 
era of chrome and plastic fabri- 
catories, despite the analysis and 
study of a whole new group of 
pseudo-scientists, whose main 
function seems to be to evaluate 
and correlate and argue at length 
with each other in the learned 
journals. 

It does not haunt those of us 
who were raised on the bread- 
board and makeshift component. 
Breakdowns were the order of 
the day. We righteously asserted 
that one could only learn by 
one's mistakes. But to a later 
generation of experimenters and 
constructors, brought up on 
ready-made receivers, and ele- 
gantly annotated kits, failure is 
taboo. 

It may seem strange that a 
manufacturer should even admit 
the possibility of failure when 
launching a product. Let alone 
publish his estimate of Mean 
Time Between Failures, which is 
what the electronics industry 
understands by those initials. 

The aforesaid pseudo-scientists 
have great fun working out the 
MTBF and juggling the figures as 
dextrously as a radio retailer 
trying to explain battery working 
hours to the rather dim purchaser 
of a portable tape recorder. 

It is becoming a modern trend 




Trying to explain to a rather dim 
purchaser. 



to admit not only that the equip- 
ment can go wrong, but that it 
will predictably continue in its 
back-sliding ways. Our postbag 
shows that many readers are not 
yet educated into this way of 
thinking. Any practising service 
engineer could soon offer a host 
of demonstrations. 

We do not have to look much 
farther than the cheaper impor- 
ted transistor radios. Except that 
a request for repair will show 
that the MTBF is either zero or 
infinity depending on whether 
the harassed salesman is sucker 
enough to accept the job, or 
shuns any responsibility. 

In the words of the poet: 
" Radios out of Old Hong Kong, 
All too frequently go wrong ". 

And the optimists who imagine 
that things will improve are due 
to be disillusioned. Already, 
rising labour rates, are worrying 
the Japanese, and have brought 
the electronics section of Hong 
Kong's labour force into the 
"elite" class. With Taiwan 
emerging as a healthy radio 
manufacturing centre and the 
great labour markets of Korea 
and India as yet untouched it 
seems likely we shall get more 
and more of the cheap and nasty 
cut-price models in the near 
future. 

To digress: a Japanese indus- 
trialist told us the interesting 
story of an argument with a taxi- 
driver whose radio blared annoy- 
ingly in the cab. He took a lot of 
convincing that Hong Kong was 
part of the wrong Empire. The 
sun will never set on shoddy 
goods — that's for sure! Of 
course, it is unfair to lay the 
whole blame abroad. There are 
too many examples nearer home. 

Henry has been taken to task, 
and is unrepentant, for dwelling 
on the maker's obsession with 
profit, to the apparent exclusion 
of reliability. Apart from the top- 
quality goods, where competition 
is for specifications and facilities 
and where high price seems an 
added attraction, most develop- 
ment seems to consist of finding 




An argument with a taxi driver. 



ways of cutting costs. 

A nodding acquaintance with 
the term " serviceability " comes 
only from the copy-writing lads, 
who see a hinged chassis or plug 
in parts and go delirious in print. 
Original reason for the hinge was 
probably that it fitted a factory 
jig or facilitated swifter inspec- 
tion. The plug and socket con- 
nectors are now mass-produced 
by astute experts who have a for- 
midable range of such products. 
and can thus supply more 
cheaply than the set-maker can 
get his joints laid in and soldered. 

There is a notorious television 
receiver with both these " advan- 
tages". Only trouble is that to 
take full advantage of the hinge 
it is necessary to partially dis- 
mantle the tuner unit and 405/ 
625 system switch, and the first 
time the serviceman tries it he 
generally manages to break the 
edge of the printed board. On 
later marks, the plug sections 
have wiring added to the back 
pins, compounding the felony. 
The l.o.t. is almost impossible to 
remove unless the printed board 
is flexed and the system switch 
rod bent. 

MTBF, in this case, is in 
inverse proportion to the amount 
of extra time taken by the service 
engineer in clearing what may 
have been originally a simple 
fault. 

Probably one of those plug 
connectors not making properly. 
Hong Kong fashion. 



A VERSATILE 

m PREAMPLIFIER 




TONE CONTROL 

by A. S. EUis 



IN the field of audio, need is often felt for an 
unspecialised preamplifier capable of being 
used with a wide variety of equipment for 
various purposes not necessarily forming a 
permanent part of any of these pieces of equip- 
ment. The particular preamplifier to be described 
was originally built to give greater sensitivity to a 
somewhat insensitive " gram " amplifier incor- 
porated in a radio receiver. The preamplifier unit 
has, however, since then been used with enormous 
success in a number of other applications. 

In the particular "gram" amplifier modified no 
variable tone controls were present and reproduc- 
tion of gramophone records tended to be some- 
what disappointing at times. Most annoying of all 
was an almost complete absence of bass. 
Accordingly the tone control box was constructed 



for insertion between the pick-up and the pream- 
plifier. The results, when all modifications had 
been completed, were astounding. Since then the 
tone control box, too. has been put to numerous 
uses, not the least of which has been that of a tone 
correction device whilst making tape recordings. 

No originality whatsoever is claimed for the 
circuits used; the preamplifier is of fully conven- 



. \Xs 



r B' r 



£ 






-WW/—! 





£ 

fe% dia. grommet holes 

B=M"dia. Coax, socket 

C=6BA clearance holes 

D=4BA clearance holes 



3V 



4» 



---T- N 






Fig. I : The circuit diagram of the preamplifier. 



Fig. 2: Preamplifier chassis drilling details (top view). 



1054 



PRACTICAL WIRELESS 



April, 1966 




Fig. 2a: Drilling and bending details of valveholder 
bracket. 

tional design, the control circuit is that used in the 
very popular Mullard two and three valve 
preamplifiers. However, the form of unit con- 
struction is somewhat novel and adds considerably 
to the versatility of both units. 

Externally Powered Preamplifier 

The preamplifier circuit is built around the well- 
known pentode type EF91. which is easily obtain- 
able In this circuit (Fig. 1) the valve consumes no 
more than about 1mA h.t. It also requires a 
heater supply of 63V at 0-3A, but both these 
requirements should easily be met without any 
overloading of the power-pack of the equipment 
to which it is attached. 

Construction of this unit was carried out in and 
around a 2oz. tobacco tin of the variety measuring 



ToC5,R2,R3. 



TbCI 



To pins 
2,6[V1) 




m SK2 output 



PRE-AMPLIFIER 
COMPONENTS LIST (Fig. I) 
Resistors: 

Rl IMO R4 2-7k£l 

R2 IMii R5 I5kl2 

R3 220k a 

All IO%iW carbon. 
Capacitors: 

CI 0-I^F paper ISOV. 

C2 0-l/*F paper 350V. 

C3 SOfiF electrolytic I2V. 

C4 0-l/iF paper 350V. 

C5 I6jxF electrolytic 350V. 

Miscellaneous: 

VI, EF9I, SKI, SK2 coaxial sockets. PL I power 
supply plug to fit socket mounted on receiver or 
other equipment, type optional. 2oz. tobacco-tin, 
size approx. 4 x 3 x I in. 

Small piece aluminium 1\ x 2£ in. One B7G 
valveholder. Nuts and bolts. 

TONE NETWORK 
COMPONENTS LIST (Fig. 4) 
Resistors: 

Rl 47k Ci R3 

R2 39k Q R4 

All 10%. £ w. 
Capacitors: 

CI S60pF 

C2 8200pF 

C3 2200pF 

C4 0-02/iF 

Potentiometers: 

VRI 250k fl log. treble 

VR2 250k n log. bass 

VR3 250k a log. volume 

Miscellaneous: 

2oz. tobacco tin, approx. 4x3x1 in., 3 miniature 
instrument knobs, SKI, SK2 coaxial sockets. 



68k Q 
6-8kft 



silvered mica 
silvered mica 
silvered mica 
paper 150V. 




Fig. 3t Preamplifier component layout and wiring. 



Fig. 4: Circuit diagram of tone control network. 

approximately 4 x 3 x lin. The lid of the tin was 
removed, later to become the baseplate of the pre- 
amplifier. The tin itself was then turned upside 
down and used as a chassis. Drilling details are 
shown in Fig. 2. It was decided not to mount the 
valve vertically on the tin as it was thought that 
wiring beneath would become unnecessarily 
crowded and inconveniently placed. Accordingly 
a piece of aluminium 2$ x 2^in. x 18 s.w.g. was 



April, 1966 



PRACTICAL WIRELESS 



1055 



«V 



i V 



B=Ji'dia 
. coax. skt. 
1* C=6BA clean 






W 1%"" 



- B © 
i 



5 ?! 
-I 

_JL| 






r^ 



5 

i 

--L- 



3fc 



Fig. 5: Tone control chassis drilling details. 

cut, drilled and bent as shown in Fig. 2a so that 
the valve could be mounted horizontally. This 
support was secured to the main chassis by means 
of 4BA nuts, bolts and shakeproof washers. Wires 
to the valveholder were taken from inside the tin 
via holes A, B and C (see Fig. 2). (Heater wiring 
was kept well away from the rest of the circuit.) 
Small components such as Rl, R2 and R3 were 
wired directly to the valveholder but the remainder 
of the components were mounted inside the tin 
out of sight (see Fig. 3 underchassis point-to-point 
wiring diagram). Earthing connections were easily 
made by soldering directly to the tin chassis. 
Power supply leads were taken through hole Dl, 
which was fitted with a rubber grommet. The 
replaced lid forming a baseplate, completed the 
preamplifier. Note: If desired a volume control 
may be incorporated in the unit by substituting a 
miniature lMfl log. potentiometer for Rl. This 
can be mounted vertically in the tin after drilling 
a suitable hole and can be fitted with a miniature 
instrument icnob. 

Preamplifier Power Supplies 

The unit appears to be fairly tolerant of power 
supplies applied to it. though an h.t. supply voltage 
of between 200 and 300V d.c. is preferable. In the 
prototype the power supply leads were terminated 
in an old Mazda octal valve base which took on 
the role of a supply plug. A similarly wired 







fig. 6: Tone control wiring and component layout. 

matching valveholder was mounted on the main 
equipment. 

Tone Control Box 

A very wide range of tone control is available 
with this circuit (Fig. 4): VR1 provides treble cut 
and boost; VR2 provides bass cut and boost; VR3 
is a volume control. It must, of course, be borne 
in mind that as with all passive tone control net- 
works there is a considerable insertion loss. 
However, if the unit is used with the preamplifier 
already described a fair excess of signal is still 
available. 

As before, a 2oz. tobacco tin was used as a 
chassis, the lid being temporarily removed to be 
used as a baseplate later. The drilling details of 
the tin are given in Fig. 5; holes A, B and C are 
for the bushes of the vertically mounted potentio- 
meters. (It is recommended that miniature potentio- 
meters be used, otherwise some difficulty may be 
encountered in fitting all three components into 
the tin.) There is ample room in the tin for all 
wiring and components may be supported on the 
potentiometer and socket connections (see Fig. 6). 
When complete and with lid replaced the circuit is 
completely screened; there will therefore be no 
hum problems. 

No difficulty should be experienced in building 
either of these units even by the newcomer to 
audio circuitry. 



PRACTICAL TELEVISION-APRIL 



L-C PICOMETER 
used with a G.D.O. this in- 
strument enables you to 
measure small capacitance 
and inductance values accur- 
ately and speedily. 



H.T. SHORTS — possible 
causes and their cures. 
FAULTY CHOKES AND 
TRANSFORMERS — A look 
at the situations where these 
are to blame for the trouble. 



TV TERMS AND 

DEFINITIONS 

Explaining in simple terms 

the definitions and phrases 

peculiar to television. 



On sale 24th March 2\- 



G.J.KING 



THE exercise was to create a pocket-sized two- 
transistor local-programme m.w. radio with an 
internal ferrite rod aerial, suitable for working 
a crystal earpiece, and that could be built easily 
from readily obtainable parts. 

While the set could have been made somewhat 
smaller than the final version, measuring about 
2\ x 2i x Jin., including the battery, this represents 
about the smallest size that can be achieved by the 
use of easily obtainable components. 

A smaller overall size could probably have been 
obtained by the use of a PP5 battery instead of the 
PP3 used, but the latter was eventually decided on 
because this is obtainable anywhere. 

Moreover, for fair performance the ferrite rod 
aerial should not be too short, and the dimen- 
sions referred to above allow the use of a 24in. 
length of i 6 in. dia. ferrite rod upon which the 
m.w. aerial coil is wound. The pick-up efficiency 
and the " Q " (goodness factor) of a ferrite rod 
aerial deteriorate as the length and the diameter of 
the rod are reduced. 

Most pocket-sized sets use a single-gang tuning 
capacitor, sometimes with a stage of " untuned " 
rS. amplification. The set to be described uses two- 
ganged tuning, one section for the ferrite rod aerial 



R3, 2-2kQ -ve line 



Regenerative 
coupling (Cx) 



fterrite R' 
rod III 1«5MQ 
aerial i 
in 
ill 




U22P32L- -i f-*-- a.>i~ i " *See 



Fig. I ^Circuit of the Reflex 2. 



and the other for the r.f. stage. This improves the 
efficiency a little above that possible by the use of 
an untuned stage. 

The Circuit 

Before the construction of the set is described, 
let us have a look at the circuit, which is given in 
Fig. I. It will be seen that two transistors and two 
diodes are used, marked (Trl, Tr2, Dl and D2 res- 
pectively). 

Now. the first transistor Trl is arranged in a 
" reflex " circuit so that it performs two functions. 
Firstly, it acts as an r.f. amplifier. That is, it has 
coupled to its base signals from the ferrite rod 
aerial LI. tuned by VC1 section of the tuning gang. 
These signals are developed in amplified form 
across the collector coil L2, tuned by VC2 section 
of the gang. From the collector of TR1 they are 
coupled to the detector circuit through C2. The 
detector comprises the two diodes Dl and D2 in 
conjunction with the input impedance of Trl. 

Thus, audio signal acts in the base-emitter 

junction of Trl. and this is how the transistor docs 

its section job. That is, it acts as an audio amplifier. 

This time, however, the amplified audio signals are 

developed across the collector 

resistor R2. From the audio 

aspect, L2 and its associated 

components have virtually no 

effect while from the r.f. aspect 

R2 is isolated by the low 

impedance presented to these 

signals by C4 and the base 

circuit of Tr2. We thus get audio 

at the junction of R2 and L2 yet 

very little r.f. signal. 

At the collector proper of 
Trl we get both audio and r.f. 
signal. The audio is somewhat 
attenuated by the r.f. coupling 
to the detector diodes, but there 
occurs a certain degree of nega- 
tive feedback which tends to 
reduce the efficiency of a single 
transistor circuit so reflexed 
below that possible by the use 
of separate transistors and 
properly isolated circuits. Never- 
theless, the extra gain possible 




by the refiexed action is well worth while in small 
receivers. , . . 4 . , _. t - 

Now the audio signal at the junction of R2 LZ 
is applied to the base of Tr2 through the electro- 
lytic coupling capacitor C4. Tr2 is arranged as a 
low-level second audio, amplifier for working the 
crystal earpiece. The audio signal is developed 
across the collector load R5 and is directly coupled 
to the earpiece via the jack socket, at terminals 1 
and 2. Terminal 3 on the jack socket serves as a 
switch so that a switch contact in the jack makes 
when the jack plug is inserted, thereby connecting 
the battery supply circuit from battery negative to 
the negative line of the circuit, via jack socket 
terminals 3 and 1. 

Switched Jack 

Miniature "switched" jacks are available but 
those investigated by the author are arranged so 
that the switch opens when the earpiece jack is 
inserted. This action can be reversed, so that the 
switch closes when the jack plug is inserted, by 
easing the spring switch contact so that it is above 
the jack contact (contact 3) which is activated by 
the plug. Fig. 2 shows at (a) the jack ?«*£»«? 
ordinarv state and at (b) the socket with the con- 
tact rearranged in the manner described above 

Both transistors run with very small emitter 
current, and this current is determined by the 
values of Rl (for Trl) and R4 (for Tr2). R3 and 
C3 serve to decouple the two stages and improve 
the stability margin. 

Trl is a Mullard AF127, which is a smaller ver- 

Switch action 

re-arranged to 

make on plug 

insertion 





(a) ^^ (b) 

Fig. 2: Modifications for the phone socket. 



sion of the AF117. The latter can be used but its 
larger size takes up most of the room between the 
tuning gang and the ferrite rod aerial. Tr2 is a 
medium gain OC71. The diodes Dl and D2 are 
miniature Mullard OA91's or equivalents. It is 
important to make sure that they are connected 
round the right way in the circuit otherwise the 
sensitivity will be impaired. 

The receiver is built on a laminate or bakelite 
panel of approximately 2| x 2lin. Most of the 
components are secured to the panel and connected 
in circuit by the use of small eyelets fitted in holes 
drilled in the panel. In addition to the eyelet holes, 
the panel carries a fin. diameter hole for 
mounting the tuning gang, two holes for L_ coil 
former, two holes for the rubber band that fixes 
around the ferrite rod aerial mounting grommets, 
two holes for the battery securing rubber band. 

Drilling details for the panel are given in Fig. 3. 
and the holes marked with " Y " are those to 
accommodate the eyelets, of which there are 
twenty-four. These holes should be of a size thai 
provides the eyelets with a fairly tight fit, the 
actual size, however, being determined by the type 
of eyelet employed. A ready drilled chassis board 
is available plus twenty-four push-fit eyelets (see 
components list). A No. 48 drill is used for the 
former fixing holes of L2. while a |.n. drill is used 
for the rubber band holes that are used tor 
securing the ferrite rod grommets and battery. 

Fie 4 shows how the holes in the panel are 
employed, and this also incorporates a point-to- 
point wiring diagram. The eyelets, it will be seen 
carry the capacitors and resistors on the left-hand 
side of the panel, also the lead-out wires of Trl 
and Tr2 (the latter in the top left-hand comer) in 
addition to the two diodes and capacitor CI (near 
the ferrite rod aerial). The broken lines on this 
diagram correspond to point-to-point connections 
made beneath the panel, while the full-line connec- 
tions are those made on the top of the panel. 

When the holes are drilled in the panel and the 
cvelets fitted, the next move should be to solder 
the components to the eyelets, after which the 
larger components can be more easily fitted, as 
each component is soldered to the appropriate eye- 
let the above- or below-panel interconnecting 
wire or wires should also be soldered These wire 
interconnections can either consist of thin l flexible 
n v c covered stranded wire or about 26 s.w.g. 
tinned copper wire covered with insulated sleeving. 
Stranded miniature p.v.c. wire was found to be tne 
best for the job by the author. 

The eyelet-connected components on the lert- 
hand side of the panel are m°u nte J vertically, and 
it is this kind of mounting that enables all the com- 
ponents (of "standard "size) to be accommodated 
on the board. The idea is to dress one of the lead- 
out wires from resistor or capacitor back along its 
length so that the two ends can then, be pushed 
into the adjacent eyelets. It is a good plan to put 
a short length of insulated sleeving over the wire 
running bv the side of the component to prevent 
any possibility of short-circuiting -^ 

A miniature soldering iron will greatly facilitate 
the various joins and prevent burning the insulated 
sleeving and components. It is important, though, 

continued overleaf 



1058 



^2— «i 



PRACTICAL WIRELESS 



Overall dimensions ^, 
approximately 2J$x2!£ 



\-^ 4K" 1 * i ^ 



text 



TT' 

%2~r 



T 



in 



rz- 







Holes 
■ for securing 
battery 
Jfcdrill 



3fcr*~ Vholes spaced % 




Holes for securing 
ferrite rod 
.•aerial 

Will 




Fig, 3: Drilling details for the panel. 



that the tip of the iron be clean and nicely tinned 
and — of course — as hot as possible. When solder- 
ing to the eyelets, the author found it best first to 
fill the eyelet holes with solder, to cut the compo- 
nent lead-out wires to the correct length, tin the 
ends and then plug them as it were, into the eyelets 
after making the solder molten with the tip of the 
soldering iron. This technique also makes it simple 
to change components and to experiment with 
components of different values. 

After the eyelet components have been soldered 
in position and the interconnecting wiring 
completed as far as possible, the two-gang tuning 
capacitor should be fitted. The large centre thread 
of the gang spindle bearing fits in the Jin. diameter 
hole on the panel, and the gang is secured to the 
panel by the large brass nut. At this stage, make 
sure that the protruding 6BA thread on one of the 
gang bolts appears at the top left-hand side of the 
chassis board. 

The next item to position is the former for L2. 
This is an ordinary bakelite or polythene type of 
component. It is secured in position by two "self- 
tapping " or " binder " screws from the top of the 
panel. The coil winding is put on later. 

It then finally remains for the ferrite rod aerial 
to be wound and mounted, for L2 to be wound 
and put on to the former and for the wiring to be 
completed. 

Aerial and Coll Windings 

The ferrite rod winding is made on top of a 
piece of thin brown paper or card itself wound 
round the rod. The card should be cut to H x 



April, 1966 

IJjin., allowing for two turns 
round the rod, giving a winding 
length of Hin. 

The winding is made of a total 
of 72 turns of 28 s.w.g. enamel- 
led-covered copper wire, tapped 
at ten turns from one end. Close 
spaced, the turns occupy almost 
the whole length of the card 
leaving a little margin at each 
end. as shown in Fig. 5. The 
turns are finally secured in posi- 
tion by means of Sellotape. The 
card former allows the winding 
easily to be slid along the ferrite 
rod to provide a small adjust- 
ment of inductance, maximum 
inductance being with the wind- 
ing midway along the rod. 

The coil (L2) is also made on 
a paper or thin card former but 
this time it is cut to measure A 
x Hin. with two turns round the 
former. It is best to hold the 
former in position with Sellotape 
before commencing the wind- 
ing, and this technique can also 
be used for the aerial winding. 

L2 consists of a total of 136 
turns of 39 s.w.g. enamelled- 
covered copper wire in four 
layers of 34 turns, each layer 
being separated from its partner 
by two thicknesses of Sellotape. 



COMPONENTS LIST 
Resistors: 

Rl I-5MO R4 I-5MQ 

R2 47kO R5 6-8k£2 

R3 2-2kfl 

All 20% miniature. 
Capacitors: 

CI Q-OOSpF (5000pF) 

C2 0-00l/xF(l000 P F) 

C3 5 M F 12V. electrolytic 

C4 5 M F 12V. electrolytic 

All miniature types. 
Semiconductors: 

Trl AFI27 Mullard (or AFI 17, larger size) 

Tr2 OC7I Mullard 

Dl OA9I D2 OA9I (Mullard) 

Miscellaneous: 

Miniature 300pF twin gang. PW./OI. Drilled 
chassis board with 24 push-fit eyelets, rubber band 
for battery. PW/02, 2$ x 5/l6in. dla. ferrite rod- 
paper former — quantity of 28 s.w.g. enam. wire — 
mounting grommets — rubber fixing band. PW'03. 

0-3in. coil former — dust core — paper former — 
two binding screws (self-tapping)— quantity of 39 
s.w.g. enam. wire, PW/04. 

Miniature battery clips, PW/05. 

Ready drilled case and back— dial— knob, PW/06. 

Crystal earpiece with lead, 3«5mm. jack plug and 
socket. 

PP3 battery or equivalent 

Small quantity of wiring wire. 
Items: PW/01— PW/06 may in cases of difficulty 
be ordered directly from R.C.S. Products Ltd.. 
II Oliver Road, Walthamstow, London. E.I7. 



April, 1966 



PRACTICAL WIRELESS 




Ferrite rod secured by elastic bands round grommets and through board 
Fig. 4: Component layout and wiring details. 



It is best to produce this winding either on a 
separate former or on the former to be used 
before it is finally fitted to the panel. The card 
former can then easily be slid over the former once 
the latter is in position and screwed down. 

The ferrite rod is held clear of the panel by two 
Jin. rubber grommets, one at each end. These are 
also used for securing the rod a thin rubber band 
passing round them and through the holes at each 
side of the panel. A similar rubber band is used 
to hold the PP3 battery to the panel (see Fig. 3). 

Finally, a thin flexible two-conductor lead 
should be made up for the battery connections, the 
ends of the conductors terminated in suitable 
connectors for the PP3 battery and a three- 
conductor flexible lead should be processed for 
connecting from the panel at the various 



Ferrite rod 




Elastic band ^^g^. \ E lastic band 

Fig. S: Method of connecting battery and ferrite rod. 



, 1059 

points indicated in Figs. 3 
and 4 to the jack socket. 
Extreme caution should be 
taken over this latter exer- 
cise to ensure that the con- 
ductors are terminated to 
the correct tags or termin- 
als on the jack socket (see 
Fig. 2). It is also very 
important, of course, to 
avoid reversing the battery 
polarity, for while this may 
not completely ruin the 
transistors it could reduce 
their efficiency and alter 
their characteristics. 

There is sufficient room 
to accommodate the jack 
socket between the ferrite 
rod aerial and Rl (see Fig. 
4, for instance), but since 
the jack socket terminals 
carry the full negative vol- 
tage of the battery, inad- 
vertent contact between 
one of these terminals and 
the base end of Rl could 
immediately destroy Trl. 
For this reason, an insula- 
ting sleeve should be 
dressed over the terminal 
end of the jack socket. 



Tuning Up 

L2 former should be fit- 
ted with a dust-iron core 
and initially this should be 
adjusted so that it embraces 
the whole of the winding 
so adjusted and with 
in the centre of the 
ferrite rod, there should be no difficulty in 
receiving the local m.w. station. To peak 
reception on this programme, L2 core should be 
re-adjusted while slowly turning the tuning gang a 
little either side of the station for optimum gain. 
While it is impossible for a receiver of this kind 
to track accurately over the whole dial, reasonable 
tracking is achieved owing mainly to the flat 
tuning of L2. However, if the set is required to be 
peaked to a more distant station the station should 
be tuned as near as possible on the gang and then 
L2 should be re-adjusted at this new setting for 
optimum gain 

A degree of feedback occurs in the r.f. stage, 
especially towards the higher frequency end of the 
band automatically due to stray capacitance. How- 
ever increased feedback can be applied simply by 
flexing a pair of thin, insulated conductors between 
the two " live * terminals of the tuning gang. This 
is shown as the " regen coupling " on the circuit 
(Fig. 1) and the coupling in physical form is clearly 
shown in Fig. 9. On no account should a d.c. 
connection exist between the two flexed conduc- 
tors, for their purpose is simply to provide a small 
variable capacitance. In the prototype, the five 



width. With L2 
the aerial winding 



— continued on page 1081 



1060 

Modulated Light Telephone 

We have experimented with .he 
Modulated Light Telephone Link 
(February issue) at school and 
have found results reasonably 
good although there was a fair 
amount of background noise and 
distortion when used outside in 
daylight. 

We discovered that a large lens 
was better for focusing the light 
beam onto the photocell than a 
parabolic reflector. The frequency 
response at 20ft. went up to 
nearly 4 kc/s. 

I would be interested to know 
if anybody else tried this and 
what their results were like. 
R. H. Boston. 

The Chalet, 

Pett Road, Pett, 

Hastings, 

Sussex. 



Copies for Sale 



I have the complete copies of 
Practical Wireless for the 
years 1959—60—61—62—63— 
64 — 65, and if any of your 
readers are interested I would be 
willing to dispose of these for a 
reasonable sum. 

All enquiries should be accom- 
panied by a stamped addressed 
envelope. 
W. R. Hebditch. 

90 Clarendon Road, 

Hove 3, 

Sussex. 

Who Wants? 

Owing to lack of space. 1 am 
forced to dispose of an amount 
of old and new radio chassis and 
components. Also I have avail- 
able P.W.'s from January 1961 to 
March 1965, and a number of 
various other magazines. 

1 am willing to give to anyone 
who cares to call, any of the 
above items. Sorry, but no letters 
will be answered. 
Nicholas Hansen. 

413 Church Road, 

Upper Norwood, 

London, 

S.E.19. 

Tapespondent Wanted 

I would like to tapespond 
with anyone of my own age (16) 
interested in Hi-Fi radio and 
popular music. 



EM EVA/ S AND. 



SINE-SQUARE WAVE GENERATOR 

|i£Li.A.'.-' 




M. k. Beeoy. 



28 Wbeatfields, 

St. Ives, 

Huntingdon. 



From Heathkit comes the IC-82U sine-square wave generator which has a 
frequency range of 20c /s to /Mc/s in 5 bands. Sine and square wave outputs 
are available separately or simultaneously and there is less than OI5^Sec. 
rise time on square wave and less than 0-5% distortion on sine wave. Separate 
output terminals and attenuators permit individual control. In kit form, the 
price is 124 10s. and assembled and tested £36 10s. 

MULLARD MINIBOOKS 

"Principles of Electrostatics" is the title of the first in a new series 
of "minibooks" announced by the Mullard Educational Service. 

Based on the successful series of filmstrips and slides produced by 
the Service, the new books are expected to become popular with both 
student and teacher. 

"Principles of Electrostatics" is a 32-page book measuring 15cm. x 
21cm. Its 13 sections each cover a particular aspect of electrostatics. 
Typical headings are: insulators and conductors; :he electrification 
theory; the gold leaf electroscope; capacitance and capacitors. 

Minibooks are available from The Mullard Educational Service, 
Mullard Ltd., Mullard House, Torrington Place, London, W.C.I, price 
2s. 6d. (including postage), cash with order. 

GRUNDIG MANDELLO RESTYLED 

Grundig (Great Britain) Ltd. announce that their popular 
Mandello Stereogram has been restyled to bring it up to date. 

For those who treasure their discs, the four speed de-luxe 
record changer incorporates a micro-lift facility. The smart 
push button radio receives v.h.f., m.w'., I.w. and s.w. (band- 
spread) and can be fitted with a decoder when stereo broadcasts 
become available. 

Two Grundig Superphon ceramic magnet loudspeakers pro- 
vide 6W of stereo power — 3W per channel — and sockets are 
provided for the connection of extension loudspeakers, stereo 
decoder, tape recorder and external aerials. The Mandello 
incorporates a dipole and ferrite aerial, 6 valves, metal rectifier 
and 2 diodes. Price is 99 guineas including P.T. 




SILVER MEDAL AWARD FOR MULLARD FILM 

The Mullard film, "Thin-film Microcircuits", was awarded a silver medal 
(1st prize) in its category at the I Oth International Festival of Scientific- 
Teaching Films, organised by the University of Padua in conjunction with 
the 1965 Venice Film Festival. Over 150 films from 18 countries were 
entered and of these 52 were selected for showing to the international 
jury. 

Britain did particularly well this year. Seven of the ten films entered 
were chosen for screening and three gained awards. 

"Thin-film Microcircuits" is a 16mm sound and colour film which 
deals with the manufacture of this new type of electronic component 
from design stage to the finished product. The film also describes typical 
applications including space vehicles, miniature computers and industrial 
electronic equipment. 

Another Mullard film, "Electromagnetic Waves — Part 2", won a 
bronze medal (2nd prize) at Padua last year. 

Both of these films were featured at the P.W. and P.TV. Filmshow 
on Feb. 4th (see page 1030). 

ELECTRONICS GROUP 
The St. Cyres Electronics Group are holding a series of meetings 
in Penarth (Glam.) the first of which was on 14th January, 1966. 

By kind permission of Mullard Ltd., this group will be showing 
a very wide range of technical films which they have issued. As 
Penarth is only about 5 miles from Cardiff, many readers may 
be interested in joining the Group and seeing these films. 

Further details may be obtained from the organiser, Mr. C. 
Bogod, "Dickens", 26 Forrest Road, T»enarth, Glamorgan. 

HAM COMPETITION 

An international competition for radio hams is being held in Tenerife. 
The competition is based on the total number of contacts made during 
a given period, between operators all over the world and those in 
Tenerife. Allowance is made for the distances involved. Prizes include 
a 20-day trip to Tenerife for two people including accommodation in a 
first-class hotel. Diplomas and Silver Cups will also be awarded. 



ELECTRIC MODERN ART 

Resembling an artistic design of 
modernistic proportions, this pattern 
is actually an industrial creation 
made by electronic engineers at the 
molecular electronics division of the 
Westinghouse Corporation in the 
USA. The pattern is to be reduced 
thousands of times until it is finally 
engraved on a piece of silicon of 
almost microscopic size. 

The microminiature will then 
become an integrated circuit for use 
in a computer. 



1061 



Any Ideas Please? 




Can any of your readers 
suggest a practical design for a 
simple transistorised audio 
generator tuning over a range of 
about 20—200 c.p.s.? 

This would be of use in tuning 
loudspeaker enclosures and 
would not require a critical 
waveform output. 
F/Lt. G. Halbert. 

Officers' Mess, 

R.A.F. Lyneham, 

Wiltshire. 

Frequency Synthesisers 

I was interested to see in the 
March issue a description by 
" Henry " of a piece of appara- 
tus known as a Frequency Syn- 
thesiser. He appears, however, to 
have grasped the wrong end of 
the wrong stick. As I understand 
it, and I have used frequency 
synthesisers, the equipment has 
nothing to do with diversity 
reception or multi-channel trans- 
mission as Henry would appear 
to believe. 

The frequency synthesiser is a 
device which combines the 
stability of a crystal oscillator 
with the flexibility of a v.f.o. It 
can give any frequency from 
lkc/s to 30Mc/s in lkc/s steps 
with an accuracy of ± 2 parts in 
10 s and is normally used by s.w. 
broadcast stations as the il. 
drive input to a transmitter. 

The basis of the synthesiser is 
a lkc/s crystal whose harmonics 
up to 30Mc/s are selected by a 
triple mixing system to give the 
required output frequency. It 
uses about 90 valves and would 
cost a wealthy ham about £1,500. 
J. N. Douglas. 

Glasgow, N.W.. 
Scotland. 

Sell or Loan 

Sir, I would be grateful If any 
reader could sell or loan me . . . 

. . . ferrite rod aerial for Cossor 524 
a.m./f.m. receiver. — T. F. Jones, Flat 2, 
Block 3, Wychbury Court, Highfields 
Escace, Halesowen, Birmingham. 

... a circuit diagram, and any informa- 
tion (i.e. modern equivalents of valves) 
etc. of the RII55A and RI07 ex Govern- 
ment receivers. — Brian Carling, A494I, 
27 Ellis Close, Cottenham, Cambs. 

. . . the circuit diagram of the Sound 
A20/038S8 tape recorder. — N. McFerran, 
58 High Street, Newtownards, Co. Down. 
N. Ireland. 

. . . the circuit diagram or service 
manual for the Air Ministry Oscilloscope 
type II Ref. No. 105/562.— R. E. Fields. 4 C 
Torkington Road, Gatley, Cheshire. 




SET 
MODS 



by S. Simpson 



Part 2 



Inclusion of output stage 

The reader should now have a highly sensitive 
receiver which, using about 10ft. of aerial, will 
provide signals all over the 4-5 to 8Mc/s dial. The 
2 to 4-5Mc/s band will be relatively quiet at the 
2Mc/s end until dusk. One does not always use a 
headset, however, so the next modification is the 
provision of loudspeaker output. 

(1) Strip all components and wiring from above 
and below the v.h.f. end of the chassis, other 
than the valve sockets and the input plugs. (If 
desired, the input plugs can eventually be 
removed and the holes blanked off but, at 
present, the h.t. and l.t. live leads must be 
retained for two more checks before the 
mains power supply is introduced. Take care 
not to damage the two-gang v.h.f. variable 
capacitors, to be used later. 

(2) Remove B GAIN and in its place, fit an 
s.p.s.t toggle switch (hereafter *' LS switch "). 
Mount the switch horizontally and ensure 
that ON entails moving the dolly towards the 
centre of the panel so that it " brings on " the 
output stage when wanted. 

(3) Check that V8A, pin 8 is earthed. Connect a 
heater lead from V8A, pin 7 to the ON 




Fig. 4 1 Output stage, showing monitor point. 



contact of the LS switch. Connect the OFF 
contact of the LS switch to V3A pin 2. 

(4) Make up the circuit for V8A as shown in 
Fig. 4. The screened, grid-input lead is con- 
nected to TS1 tag 4A (already carrying a 
phone output 'lead; the lead remains there). 
The screen is earthed at TS1, tag 3. 

(5) An output transformer was set aside earlier. 
This should now be fitted adjacent to V8A 
(Fig. 2). The blue terminal is connected to 
V8A, pin 3. green to TS1, tag 9, red to one 
lead of a lOin. length of twin cable, and 
white to the other lead; white is also earthed. 

(6) Remove the KEY socket; note the required 
contacts to adapt the KEY socket to serve as 
a non-self-shorting loudspeaker plug. Connect 
the twin output lead to these contacts, then 
refit the socket 

(7) Fit one of the two 6V6 valves (supplied with 
W.S.19) to V8A socket. Connect the loud- 
speaker to the LS plug and insert the plug 
into the LS (formerly KEY) socket. 

(8) Set up the receiver for phone operation, and 
when assured signals are being received, set 
the LS switch to ON. The loudspeaker 
should operate after the usual warm-up time 
for V8A. Switch off LS and check the loud- 
speaker output fades out 

Inclusion of band-spread 

The tuning drive on the four-gang capacitor is 
quite slow, but although satisfactory between 2-5 
to about 3-5Mc/s, signals whip through the dial 
rather swiftly at higher frequencies. A very satis- 
factory band-spread can be incorporated using 
existing material, but entails a fair amount of dis- 
mantling of the P.A. tuning arrangement. 
(1) Dismantle the P.A. tuning drive as under: — 

(a) Remove the central screw on the FLICK/ 
SET control; remove the knob. 

(b) Remove the four flick pre-set screws from the 
centre-piece on the P.A. TUNING dial. 

(c) Remove two 4BA screws securing the 
complete drive and capacitor assembly to the 
chass ; s. The assembly should now be loose, 
but not yet removable. 

(d) Remove one 4BA dome-head screw securing 
the slow-motion drive assembly to the panel. 



April, 1966 



PRACTICAL WIRELESS 



T063 



EXCLUSIVE TO PRACTICAL WIRELESS READERS 



TRANSISTOR 

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WITH LOUDSPEAKER 



BULK PUR- 

CHASE EN- 

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The "BAN 

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NO MORE TO PAY ££ &£ ^£ 

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pocket, or handbag. Worki" for months oBlfM. 
battery. Should la-t a lifetime, anyone can 
assemble it in an hour or two with our easy plan. 
Miniature -peaker — everything, only iiS/6. 'ift 
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ONLY 



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READY BUILT 
LIMITED QUANTITY SAVE £3.16.6 




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Robustly made, brand new 
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A fit t separate, fully transistorised 
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Mr R. O'D of Londonderry, writes:— 
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RADIO COURSE. Orginally £6 SEND 
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IT HAD TO COME EVENTUALLY- THE 
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World-wide short-waves reception lucludliiic 
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Take it anywhere — 
it's featherweight! 61n. 
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within 2 hours— only 
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Parts inc.. Case, Personal phone. Easy-to-follow 
plan— 49/6, plus 3/6 Post, eto. 





^i-«. MINIATURE CDV 

■a-SgaTj precision Jrl 

' CAMERA 



Only 



12/6 



2/6 

Offered at a fraction o[ its Real Worth. Brand new 
precision made photographic Instrument in chromed 
steel and leather. Two speed shutter. 2!in. x ljin.! 
Easily concealed in i'alm-of-haudl and takes crystal 
clear photographs. The rage of America and offered 
at the absurd price of 12/6. Incl. solid leather case — 
■<M 6/- for pack of 6 films which give 60 photos. 
superb craftsmanship to miniature. Send imme- 
diately. 




CAR CIGARETTE 

LIGHTER 
DISPENSER 

.7 Hi?h Class Stores sell a' 

4 3 ens. — save £2.4.6. 

Top quality chromium. 

Car cigarette lighter 

\\ — Dispenser. Fixed in a jiffy — 

_ M , Y Pressing Button delivers ready-lit 

OrNLT cigarette Into your hand: Takes 

IQf z 10 cigarettes— King size or any size: 
Qf Q As fitted to luxury oars. Safe, fool- 
proof. 3} x A x lln. Lifetime tested, 
ready to ase Relnnd it not worth 3 gns. 750 only. 
18/6 plus 1/6. P. & P. (state 6 or 12v.l. 



vW ; 



AUTOMATIC 
POCKET CALCULATOR 



Adding and Subtr 
your Bngei tips 



cling up to 999,009 



ONLY 



8/6 



This superfast, lightweight calculator is 
simple to operate yet fantastically accurate. 
Precision engineered by craftsmen and 
factory tested for reliability. Ideal for use 
in Office.- Shops, Stores, Daring Games, 
etc. Complete with carry case. Slips easily 
into the jacket pocket or purse. Decimal 

tables, included for engineers — A terrific bargain 

that you'll enjoy using. 



Read what just a lew ol our Satisfied customers say 

R.C. of Harringay writes Received with 

thanks Skyromo . . . Very pleased. Working 

well 

B.M. of Harrogate writes . . . / would 

like to thank you ... It was a real bargain. 

L.S. of London W.8 writes . . . given H 

a good try out and I am very pleased with 

the results. 

S.B. of Somerset writes . . . delighted 

with this radio . . . glad if you could send 

one more. 

T.F. of Stevenage writes . . . / would just 

like to say how pleased my son is with this 

radio. 



WORE TERRIFIC OFFERS 
FROM CONCORD! 



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All the latest refine- 
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this new MULTI 
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radio — the Internal 
aerial picks up even remote stations and 
the powerful built-in speaker gives room 
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—packed in original manulacturers car- 
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Send 35/- Plus 4/6 P. «v P. 







NEW RADIO 

NO SOLDERING 

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ANYONE 

CAN BUILD 

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19/6 

EVEN THE OLDER CHTLDREN 
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16 connections! then hear it reach out 
bringing in station after station, loud and 
clear. Palm-of-hand size 4j x 2j x liin. 
Many Testimonials: M.H. of Bradford, 
writes: " . . . / have fust completed one of 
your sets successfully, it is the first time I 
have ever tackled anything like a radio, and 
I must state here and now. I am amazed how 
easy it is to a layman like me. Your instruc- 
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Manufacturers to You. Send 19/6 plus 
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PARTS AVAILABLE SEPARATELY 



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RADIO 



18/6 




Yes a perfectly ordinary packet of 

cigarettes! — but watch your friends 
astonishment on hearing it fetch in 
station after station, loud and clear! 
Still holds 10 cigarettes — yet cleverly 
conceals highly sensitive, fully transistor- 
ised circuit (including tiny .battery). 
Even a young boy can assemble It in under 
2 hours. No soldering. No experience 
necessary. Only 16 connections to make. 
Ideal for taking to work with you. From 
our bulging testimonial file. Mr. D. B. of 
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PARTS AVAILABLE SEPARATELY 



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LTD. (DEPT. P.W.30) 77 NEW BOND ST. 



LONDON, W.1 



1064 



PRACTICAL WIRELESS 



April, 1966 




MINT TRANSCEIVER 

The latest craze - . 
Push- button opera- 
tion; crystal control. 
Kully transistorised 
(3-tran*istor circuit) 
(or perfect reception. 
Trem«n.|on» OOBK 
mercial scope. Cony 
plete with strap, bat- 
tery and 8-»ectlon 
antenna. 'see 9v. 
PP.1 battery and 
operates up to half 
mile tn open country. 
Measures 6Jln. x 

2lln. x ljin. Frequency 27.126 

Me/a. 

OKiT M.19.9 Pair. 

'Post and Insurance. 4/6). 

More powerful models available. 



HINT PORTABLE 

TAPE RECORDER Mk. II 

Now, a 
reasonably 
priced, small 
portable 
tape recor- 
der that, 
gives excep- 
tional re- 
starts- Precision-engineered through- 
out. Hand microphone has thumb 
switch for automatic stop/start/ 
record/playback etc. Ideal sales 
reports and dictation etc. Tough, 
unbreakable fawn plastic case witb 
deck cover (or mobile recordings. 
Complete with earphone, tnierc- 
phone, tape, two (00018, batteries. 
9iie8x7J i it in. Usually £12.12.0 

OTJB PRICK 16.15.0. 
(Pot! and iniuranee 4/6) 

BATTERT/MA1N8 model, 990- 

360v. J7.15.0. 

(Past and uuuronei «/6). 



ELECTRAMA 




WINDMILL HILL 



HAILSHAM 



SUSSEX 




Bargain of the Month 
Save £7 ! ! 

Benkson 4-way Intercom 

Bulk purchase has cut retail prloc 
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sub-stations with built-in call 
system. Absolute privacy to each 
extension. Push-button control. 
Crystal clear reproduction through 
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junction box, Instructions, etc 
67.10.0 (Po« and inturanee 5/-). 

CLEARANCE OFFER I 

SOLDERING IRONS 

230/2SQV. copper bit and rapid heat 
element. Ideal printed circuit work 
11/6 iPatl and Inturanee 2/-). 



AMPLIFIERS 

Two Valve AmpHner for portable 
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23.18.6 (Post and insurance 3/6). 
Linear L 45A, 3-valve amplifier 
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reproduction at a realistic price. 
£8.10.0 1 Pot! and Iniuranee 5/8). 
Stereo 2-valve amplifier using 2 
UCL82 valves. Mono/stereo con- 
trol switch with tone control etc 
Absolute snip. 
£6.12.8 (Pott and inturanel 5/6). 



WESTROf. 

TELEPHONE 

AMPLIFIER 

waited years for 
this! Just Insert PP3 bat- 
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to side of 'phone, and an 
incoming call is amplified. 
No need to stop work wait- 
ing for numbers to answer! 
Used witb tape recorder (e.g. 
MINY. see above), perfect record- 
ing of conversation can be made. 
Ideal field sales reports. 
ONLY 59/8 1 Post and inturanee 4/-). 




TRANSONIC 
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The very latest 1866 Tran- 
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STEREO CABINETS £3.10.0 
(Poll and inturanee 5/-) 

Vest Pocket MULTIMETER 

Measures A.C./D.C. 0-1000 v., 
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current 150 niA. liesl«tanoe 100 k 
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BATTERY ELIMINATOR 

Easy-to-fit eliminator takes the 
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PP3 Model 17/6 PP0 Model 26/- 
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RETAIL SHOP 

ELECTRAMA. 46 Windmill Hill 
RUISLIP. Tel. 5780 



THE 

PEMBRIDGE 

COLLEGE 

OF ELECTRONICS 

PROVIDES TRAINING 

IN RADIO 

AND TELEVISION 



FULL-TIME COLLEGE COURSE 
IN RADIO AND TELEVISION 

Our Course has now been extended to sixteen months' 
duration to include theoretical and practical instruction 
on transistor television receivers, U.H.F. television re- 
ceivers and colour television. 
Next course commences 19th April, 1966. 
This Course is recognised by the Radio Trades 
Examination Board (R.T.E.B.) for the Radio and 
Television Servicing Certificate examinations. 
Provides excellent practical experience on valve 
and transistor radio receivers and all well-known 
makes of television receivers. 



To: 

The Pembridge College of Electronics (Dept. P11) 
34a Hereford Road, London, W.2. 

Please send, without obligation, details of the 
Full-time Course in Radio and Television. 



Name. 



Address. 



_ 



April, 1966 



PRACTICAL WIRELESS 



(Note that there is a stout 
leaf spring holding the slow 
motion spindle against the 
edge of the engraved dial.) 
Remove the drive assembly. 
(e) Loosen the grub-screw in 
the side of the dial centre- 
piece: it should now be 
possible to separate the dial 
from the flick-stop assembly; 
this will expose a small 
tapered pin which passes 
through the collar of the 
flick-stop stub-flange and 
the capacitor shaft. This 
collar (not the pin) is 
required for the modifica- 
tion and the pin must there- 
fore be removed. (Note that 
the pin is fairly soft and 
easily burred. One way of 
removing it is to cut away 
the tapered end with a 
hacksaw and punch out the 
remainder.) 

(D Summing up the results: One should have 
available the slow motion drive and attaching 
4BA dome-head screw, the engraved dial 
riveted to a metal disc to which the centre- 
piece is attached by one 4BA dome-head 
screw, the collar and stub-flange removed 
from the capacitor shaft. At this stage it is 
advisable to prepare a new dial to replace 
the existing engraved plate, which can be 
removed by withdrawing the 4BA screw from 
the centrepiece and drilling out the four small 
rivets securing the plate to the metal disc. 
In the author's version a circular disc of thin 
card and of the same diameter as the 
engraved plate was marked with 30 equi- 
distant divisions around one semicircle and 
Letraset numerals 1, 5, 10, 15, 20, 25 and 30 
attached at the relevant divisions. The centre 
of the card was removed to almost the 
diameter of the underside of the centrepiece, 
then the card disc was secured to the metal 
disc, using Cowgum. The centrepiece was 
then refitted to the metal disc to complete the 
dial assembly. 

(2) Earlier the reader removed the v.h.f. two- 
gang capacitor mounting plate. This assembly 
is now used as the bandspreader. Fit the 
collar to the capacitor shaft and insert the 
collar through the panel aperture formerly 
occupied by P.A. TUNING; leave the 
mounting plate as it stands for the moment. 

(3) Fit the dial to the collar (note the flat on the 
collar which mates with the dial). Fit the 
slow-motion drive to loosely mate with the 
dial. 

(4) By trial assess what shimming is necessary 
between the bandspreader mounting plate and 
the receiver chassis to obtain adequate slow- 
motion drive on the dial. Also check for posi- 
tioning of the capacitor for all-round smooth 
drive. Mark the chassis, remove the capacitor 
assembly, drill and tap the chassis (there is no 



1065 



ToHX 

wiring 







Fig. 5: Power supply circuit, showing monitor points and h.t. control. 

access for nuts under the chassis), then fit the 
complete assembly. 

(5) Set the dial to 30 opposite the right-hand 
index mark. Fully enmesh the capacitor 
vanes, then lock the capacitor shaft, using the 
grubscrew accessible in the stub-flange. 

(6) Strap both sets of fixed vanes and leave 
approximately lOin. tail on the lead. 

(7) At the four-gang capacitor unsolder and 
remove the compression trimmer at OSC 
(marked on top of the capacitor plate). Pass 
the band-spreader tail through the trimmer 
hole, assess and cut the length to reach the 
rear connection, i.e. to the fixed vanes. With- 
draw the lead, prepare and heavily tin about 
iin. of the tail, reinsert the lead and solder it 
to the rear tag. 

(8) Set up and check the receiver to try out the 
bandspreader. Note that it has little effect 
around 2-3Mc/s but is extremely useful at 
higher frequencies, drawing "attention" to 
dozens of c.w. signals usually unnoticed with- 
out band-spreading. 



Inclusion of Power Supply 



The reader, running through this article as " some- 
thing to read ", may wonder why a mains power 
supply has been left so late: the reason lies in the 
weight of the W.S.19, even as found, and the 
lifting and turning necessary during the preceding 
changes. If a power supply were added as an 
early step the work of the succeeding steps would 
be quite laborious. To add the power supply 
proceed as follows: 

(1) Obtain a top-of-chassis mains transformer to 
supply about 250V at 50mA, 63V at 30A, 
5V at 2A. also a smoothing choke giving 
about 10H at 50mA. A smoothing capacitor 
assembly providing 8,uF and 16/xF at 300V 
working, a 5Z4 rectifier and a three-way 
tag-board complete the components list. 

(2) The circuit diagram is standard and given in 
Fig. 5. The locations of the components are 
shown in Figs. 1 and 2. 



1066 



PRACTICAL WIRELESS 



April, 1966 



(3) The mains input lead terminates on the three- 
way tagboard (if possible attached to the 
choke) which will carry a flat-twin mains 
lead to the A SET switch. 

(4) Dismantle the two-way switch assembly to 
gain access to A SET and B SET switches. 

(5) Cut the existing lead on A SET passing into 
the W.S.I 9 power input plug cableform. 
Parallel-connect the freed contact on A SET 
and its neighbour at that end. Add one wire 
of the flat-twin mains lead (sub-paragraph 3) 

to the parallel connection. 

(6) Remove the l.t. connection at the other end 
of the switch, parallel the two tags at that 
end and add the remaining wire of the mains 
lead. 

(7) Ensure that all l.t. leads (less that passing 
into the W.S.I 9 power supply cableform) 
which were associated with the A SET l.t. 
connection are still in good contact. Fit a 
short length of sleeving over the common 
connection and tuck safely away. 

(8) At the B SET switch remove the lead pass- 
ing into the W.S.I 9 power supply cableform, 
cut the lead short at the power input plug. 
On the B SET remove the lead supplying h.t. 
to the circuitry and connect it to the tail 
from the smoothing choke (see Fig. 5). 
Connect the contact on B SET, just cleared, 
to chassis. Connect the contact which 
carried the W.S.I 9 h.t. lead to the centre tap 
of the h.t. winding on the mains transformer. 
The B SET switch now provides means of 
disconnecting h.t. while the heaters remain 
active. 

(9) At the remote end of the mains supply cable 
check for continuity between leads with A 
SET " on " and open-circuit with A SET 
"off". Check for open-circuit to chassis 
with A SET in both positions. 

(10) Connect a voltmeter (to read 300V) between 
the smoothing choke output and chassis. 

Ml) Ensure A SET is switched off and l.s. is also 
off. Connect the mains supply cable to a 
power outlet. Switch on A SET and B SET 
and note that the valve heaters are alight. 



Watch for the developing h.t. in the volt- 
meter. Switch off A SET. 

(12) PIut in the headset, turn up A GAIN and 
R.F. GAIN. Connect the aerial and switch 
on A SET. Check the receiver functions 
normally, then turn down A GAIN to mini- 
mum and check for hum on the h.t. supply. 
If all is well switch off; if hum is present 
make the usual checks of capacitors, leaking 
cathode insulation and so on. 

(13) Fuses. If it is desired to fit fuses a panel 
fuse to carry h.t. can be installed in the 
QUENCH aperture and another may be 
fitted in the rear wall of the chassis to carry 
mains input. The h.t. fuse should be connec- 
ted in the earth return from the h.t. winding 
of the mains transformer (Fig. 5). Suitable 
fuses would be 250mA (h.t.) and 2A (mains). 

Monitoring system 

The inclusion of a monitoring system is a fairly 
simple task but, in a complex receiver, an addition 
well worth having. The system involves a nine- 
way single-pole wafer switch instead of the 
existing five-way double-pole component and uses 
the existing meter. The monitor system is shown 
in Fig. 6. 

(1) Remove the panel meter and clamp assembly 
held by one 4BA screw passing through an 
eyelet on the clamp. 

(2) Remove the clamp from the meter by 
loosening an 8BA screw at the top of the 
clamp. 

(3) Using a 10,000fi series resistor check the 
meter on a 15V supply for continuity. If 
satisfactory proceed to step 4 and then to 
step 7. If the meter is faulty continue as 
follows (these instructions are based on the 
author's findings on a faulty meter and the 
fault may be common in these meters, now 
several years old). 

(4) Withdraw three small screws from the side 
of the meter case, withdraw the meter from 
the case and ensure the needle is free to 
move. 




Monitor rectitier output 
Monitor smoothed H.T. 



Phone 



Mixer 
6K8 



TMonh 
mixe 
bias 



1KT.1 



Monitor 
mixer 
bias 



Monitor 
AG.C 



IF.T.2 



Detector 
AWC. 
AK1 



I I 



} 



Monitor 
AF. 
bias 



to. 



L 



Mixer 

osc. 

part 6K8 



Monitor 
osc. 
KT. 



BFO. 



J 



■ J F tkkwoM- - 



1 



US. 



Output 



Monitor 

output 

bias 



/ 



Power 



23ov 

60W 



B.RO. bias 



Fig. 6: Monitoring system in modified WS.19 receiver. 



April, 1966 



PRACTICAL WIRELESS 



1067 



PESPATCH-TOPA Y7-PHONE-R.C.S.? 

NEW ELECTROLYTICS FAMOUS MAKES 

TUBULAR TUBULAR CAN TYPES 



DE-LUXE PLAYER KITS FROM £10 ! 



U: 



Autoohange 2-Ione 
Cabinets 17 x 15 x 
Blin. High flux 
loudspoakor. 3 watt 
i n m o u s make 
amplifier ready built. 
Quality output. Volume 
and Bass controls, 
items at 
together 
perfectly. 
Special in- 
structions 
enable as- 
sembly in 
30 minutes 
0nly5wires 
to join. 12 
months' guarantee. 

SINGLE PLAYER KITS 
BSH Junior £10. 0.0 
BSR GU? £11.10.0 

GarrardSRP12 £11.10.0 
liarrnrdSP25 £17. 0.0 




ALL 
POST 
FREE 

AUTOCHANGE KITS 
BSR Monaroh £11.10.0 
Garrard 1000 £12.10.0 
GarrardMod.50 £14.10.0 
Garrard AT60 £16.10.0 



Or Separately: Pit 
3 watt amplifier i 
ADTOCHANGE UNITS 
BSR Monarch £5.10.0 
Garrard 1000 £6.10.0 
Garrard 2000 £7.10.0 
Garrard 3000 £8.10.0 
Garrard Mod. 50 £9. 0.0 
Garrard AT60 £11. 0.0 
Garrard A70 £21. 0.0 



yer Cabinet £3.10.0 
rith spoakor £3.10.0 
SINGLE PLAY UNITS 
BSR Junior £3.10.0 

BSRGU7 £5. 0.0 

Garrard SRP12 £6. 0.0 
TRANSCRIPTION UNITS 
Garrard SP25 £11. 0.0 
Garrard LAB80 £25. 0.0 
Garrard 401 £30. 0.0 



Q MAX CHASSIS CUTTER 

Complete die punch Allen screw and key 
iin. I4'6 l-trin- 18'- Ifin. 22'6 



1 4 '6 
I5'6 
IS'9 
18'- 



IJin. 
I Jin. 
Ifin. 
llin. 



18'- 
1 8'6 
20'- 
20'6 



2in. 
2A'n. 
2%in. 
lin.sq. 



34'3 
37'9 
44'3 
31/6 



CRYSTAL MIKE INSERTS 

liln. dla. x iin.. 6/6: BM3 1 x jln.. 7/6: 
ACOS mic, insert Uin. dia. x Jln. 8/6 
TA.VSOY CARBON MIKE complete. 8/6 



Colls Wcarite "P". 4/-; Osmor "Q" from 4/-. 
Rep. DRR2 L. & M. with reaction, 4/6. 
Ferrite Aerials Valve. M. 8/9: M.L.. 12/6. 
Fcrrlte Aerials. L. & M. for transistor/ 
circuits. OSMOR, 10/-. \VEYRAI>, 12/6. 
JrcrritoRo<18x;m..6x2in.,6x*/ IC in.. 3/-ea. 
M.F. Choke, 2/9. Osmor <|CI, 6/9. 

Test Prods, 4/6 pr. Set Trim Tools, 3/-. 
Neon Mains Tester Screwdriver, 5/-. 
MultlCOre Solder, 6d. yd. Dispenser, 2/6. 
VALVE HOLDERS. Int. Oct. 6d. Mazda Oct. 6d. 
B7«. BSA. B8G, B9A, 9d.; B70. BOA Cans. 1/-. 
Ccranilu I.O. EF50. BG7, BOA. 1/-. Valve plugs 2/3. 



I.F. TRANSFORMERS 7/6 pair 

466 Es Slug Tuning Miniature Can. 3 x I, "in. dia. 
High Q and good band width. Data supplied. 



MOVING COIL MULTIMETER TK !0a 

0-lOOOv. A.C/D.C. ohms. to 100k. etc.. 47/6. 
MOVING COIL MULTIMETER EPI0K 
0-lOOOv. A.C/D.C. ohms to 3 mefr. etc. 79/6. 
MOVING COIL MULT1METEK EP20K 

0-2500V. D.C. O-lOOOv. A.C. 20.000 ohms per 
volt. to 6 meg-. 50 Microamps. 99/6 

MOVING COIL MULTIMETER EI'.iOK 
0-1200 D.C./A.C. volts. 30,000 ohms per volt 
to 10 meg. 23 microamps. 132/6 




Three Wavebands. Five Valves ECH81. 

Long. Mod.. Short. EF89, EBC81. EL84. EZ80. 
12-months guarantee. A.C. 200/250v. Ferrite 
Aerial, 5 watts, 3 ohm. 13jin. 1 7in. high x 5in. 
deep, Dial size 13 s 4in. horizontal wording. 
Aligned, calibrated. Chassis isolated Irom mains. 

BRAND NEW £10.10.0 Post Free 
With BA KER lgin. loudspeaker £15.10.0. ' 

VHF-FM RADIOGRAM CHASSIS £18.10~0 
With Long and Med. Wavebands, 15in. x 7in. x 8in. 



1/350T 2/- 

2/350v 2/3 

4/350v 2/3 

8/450v 2/3 



100/25V 
850/BSi 

500/lSv 
2000/SOv 



16/450v3/- 8^8/450v 



32/450v 3/9 
25/25v 1/9 

50/oOv ■>!- 



2/- 
2/8 
2/6 
11/6 
3/6 



8-16/450* 3/9 
16-16/450v 4/3 
32-32/350V 4/6 



8/600V 

16/600V 12/- 

16 + 16/500T 7/6 
32 + 32-1- 32/350V 6/- 

32 + 32/450v 6/- 

50 + 50/350v 71- 

64-120/350V 11/6 

100 200/275V 12/6 



PAPER TUBULARS 
350v. 0.1 9d.; 0.5 1/9; 1 ml'd. 3/-; 2mFd, 150v. 8/- 
500v. 0.001 to 0.05 9d.: 0.1 1/-; 0.25 1/6, 0.6 2/8, 
l,000v. U.001, 0.0022, O.0O3.1, 0.0047, 0.01, 0.022, 
1/6; 0.047, 0-1. 2/-. 0.2a, 0.47. 3/-. 
2,000v. 0.005. 0.01, 0.0-2, 2/6: 0.05, 8/6. 
Snb-Min. 0.001. 0.005. O.01, 0.02, 0.04, 0.05, 0.1 1/- 
Snb-Min. Eleotrolytics 1, 2. 4, 5, 8. 16. 25, 30. 50, 
100. 500. 1.000 mFd. 15v. 2/6. 1,000 mFd. 50v. 7/6 



SILVER MICA itolerance lpIO. 2.2 to 47pF 1/-: 
dtttc % 50 to 800 pF, 1/-; 1,000 to 5.000 pF, 2/-. 
CERAMICS BOOT., lpF to 0.01 mFd. 9d. each. 
TWIN GANGS. "O-O" 2(18 pF + 17fl pF, 10/6; "O" 
365 pF min., 10/-; 500 pF standard with trimmers, 
9/6; midget with trimmers, 9/-; 500 pi" slow motion, 
standard, 9/-; small 3-gang 500pF, 19/9. Single 
"O" 305 pF, 7/6. SHORT WAVE. Single 10 pF, 
25 pF, 50 pF. 75 pF, 100 pF, 150 pF, 5/6 each. 
Can be ganged together. Couplers 9d. each. 
TUNING AND REACTION. J 00 pF, 300 pF. 500 pF, 
8/6 each, solid dielectric. TRIMMERS Compression 
ceramic, 30, 50. 70 pF, 9d.; 100 pF, 150 pF, 1/3; 
250 pF, 1/6; 000 pF. 750 pF. 1/9. 
HEADPHONES. 2.000 ohms, 12/6; 4.000 ohms, 15/-. 
EL34 Translormer De Luxe, Push-Pull 30w.. 90/-. 
EL84 1 510) Ultra Linear Pusb-Pull, lOw, 49/6. 
lOw. Multi-ratio Push-Pull. 18/6. EL84 3-3), 25/-. 
Standard Pentode. 5/6. NEW ELL30 12w., 25/-. 



TRANSISTOR MAINS 
ELIMINATOR PPI-6v. PP9-9v. 29/6 

DOUBLES 42/6. PPl+Pl'l, PP9+PP9, PP11 
(4) +44) Size as Batteries. Also min. 9v. 19/6. 



WEYRAD PS0 COILS 

Ferrite aerial 12/6: Osc. P50/1AC. 5/6; 1st 
and 2nd I.P. P50/2CC. 5/7 each; 3rd I.F. 
F50/3CC. 6/-; Driver Trans-LFDTl. 9/6. 
Printed Circuit 9/6: 35 ohm Sneakers. 5in. 
17/6: 6x4in. 21/-. Bock 2/-. 3 ohm OPT 10/6 



NEW MULLARD TRANSISTORS 

Holders 1/3; OA81, 3/-; 0C71, 8/-; OC72, 7/6,- 
OC81, 7/6: AP115. 10/6: AF114. 11/-; OC44, 8/-; 
OC45. 8/-; OC171. 9/-; OC170, 8/6; AF117, 
9/6: OC26, 12/6: ORP12, 12/6. 
SILICON RECTIFIERS. OA210 500mA, 200v„ 5/6: 
BY100 550 mA. 400v.. 10/-. 



MAINS TRANSFORMERS. PoHa t e 2/- each. 
STANDARD 250-0-230: SOmA, 6.3v., 3.5a., 
tapped 4r,, 4a. Rectifier fi.3v., L, 5v. 
2a., or 4v. 2a. 25/-; <li( to 350-0-350 29/6 

MINIATURE aOOv., 20mA, il.3v., la, 10/6 

MIDGET SBOv- 45mA., 6.3v.. 2a, 15/6 

SMALL 300-0-300 70iuA., 6.3v„ 4a, 19/6 

E.M.I. 280-6-280, 100mA. fl.Sv. 3.5a, 6.3v. l}a 17/- 
HEATER TRANS. «.3v.. l»a., 7/6; S.3v. 4a. 10/6 
Ditto, tapped 1.4. 2. S, 4, 6. fi.Sr., lja. 8/6 

GENERAL PURPOSE LOW VOLTAGE 2 amp. 
3, 4. 5. 6, 8, 9. 10, ]->, 15. 18. 24. 30v. 25/- 

ap. version, taps and C taps up to 60 v. 29/6 
AUTO TRANSFORMERS. 23fl-110v., 60w. 18/- 
0-115. 200. 230. 240v.. 150w, 25/-; 500w, 82/8 
MULLARD "510" Mains Translormer 33/6 

TRANSISTOR 9v.. ROmA., 1} x 1} x Iin. 7/6 



BEST BRITISH P.V.C./Spare ") I f. \ 
RECORDING TAPESySpools^/ *> ea J 



LP 5in. 900ft. 11/6 
LP 5! in. 1200ft. 14/6 
LP 7in. ISOOft. 19/6 



DP 5in. 1200ft. 18/6 
DP Siin. ISOOit. 24/6 
DP 7in. 2400ft. 29/6 



Volume Controls 

or Log Tracks, 
spindles. Midget 
5 K ohms to 2 Meg. 
L.S. 3/-. D.P. 5/- 



Line 
Long 



8tcreo L'S 10/6; DP14/6 
1m log— lm A. 'log. 7/6 



iin 



CABLE 
Be mi-air spaced 
40 yds. 17/6 Rri . 
60 yds. 25/- 00. yd. 

Ideal 625 lines U.H.F. 
Low loss 5dB .. ,_ . 

lQ.)lt.500Mc'a I /PyO. 



TELESCOPIC CHROME AERIALS, 12 to 33in., 6/8 
TRIPLEXERS Bauds I.n.UI. 12/6. COAX PLUGS 1/-; 
LEAD SOCKETS, 8/-: PANEL SOCKETS. 1/-. 
OUTLET BOXES (Surface or flush). 4/- each. 
BALANCED TWIN FEEDERS. 6d. yd. 80 or 300 ohm 
TWIN SCREENED. 1/6 per yard. 80 ohms only. 



THE "INSTANT" BULK TAPE 
ERASER AND RECORD HEAD 
DEMAGNETIZER 2(io/250v. A.C- 35'- 



BAKER LOUDSPEAKERS 

HANDMADE BY CRAFTSMEN 
HIGH FIDELITX 
MODELS 
12in. STALWART 15w. 
3 or 15 ohms £5. 5 

12in. STANDARD £8. 
12in. DE-LUXE £9. 
12in. BASS £12.10 

12in. SUPERB £15. 
15in. BASS £18. 

LABORATORY 
STANDARD MODELS 

12in. with D.W.L £28.10 
15in. with D.WJ. £28.10 

A'BW CA I A LOG VB FREE I 

GROUP MODELS FOR VOCALS 
BASS LEAD and RHYTHM GUITARS 
Frequency response 30-10,000 cp.s. 
Voice Coils 15 ohms. Heavy Duty outputs. 
•'GROUP 25" 12in. dia., 26w.. 12,000 lines 5 gns. 
"GROUP 35" 12in. dia., 35w., 14,000 lines 8} urn. 
'GROUP 50" 15in. dia., 50w., 17,000 lines 18 rrns. 




LOUDSPEAKERS P.M. 3 OHM FAMOUS MAKES. 
2iin., 3in., 4in.. 5in., 7 s 4in-. 15/6 each; 8ln., 17/6; 
6jln„ 16/6; 10in., 30/-: 12in., 30/-; (15 ohms. 35/-); 
10 x 6in.. 22/6; 8 x 3in.. SI/-; 8 x 5m., 21/-. 
EMI 13 x 8ln. ceramic, double cone. 3 or 15 45/-. 
WAVE-CHANGE SWITCHES, 2 p. 2-way or 2 p. 
8-way; 3 p. 4-way or 1 p. 12-way: 4 p. 2-way or 4 p. 
.(-way. 3/6 each; 8 p. 4-way, on 2 wafers. 6/6. 
WAVE-CHANGE "MAKITS" available, 1 p. 12-way. 
2 p. 6-way, 3 p. 4-way, 4 p. 3-wav, 6 p. 2-»av. Kit 
Price: 1 wafer 8/6; 2-wafer 12/6; 3 wafer 16/-. Extra 
water* 3/6 each, extra long shafts 2/- extra. 
TOGGLE SWITCHES s.p. 2/-; d.p. 3/6; d.p.d.t. «/- 



•RADIO BOOKS • (P.P. 9d.) 

\ alves. Diodes, Transistor equivs. 10/6 
Transistor Audio Amplifier Manual 6/- 
Shortwave Transistor Receiver . . 51- 
Iterrinners' Modern Transistor Sets 7/6 
Suli-niiiiiatnre Transistor Receivers 5/- 
Boy$' Book or Crystal Sets . . . . jj/6 
Milliard Maintenance Manual .. 16/- 
Iliel" Fidelity Speaker Enclosure 5/- 

TV Fault I 1 iidi 11 e 6/- 

Mtillurd Amplifier Manual .. .. 8/6 
Valve Guide, Books 1. 2, 3. 4 or 5 5/- ea. 
Practical Radio Inside Out. . . . 4/6 
Transistor Communication Sets . . 6/- 
Translslor Controlled Models .. 7/6 
International Radio Stations List 2/6 



JACK SOCKETS. Standard 2/6, closed circuit 4/6. 
Cniiulln typo 3-pin 1/3; Standard Lead Type 6/-. 
Phono Plugs II-. Socket 1/-. Banana Plugs 1I-. 
JACK PLUGS. Screened 3/-. Groudlg 3-pin, 3/6. 
BULGIN NON-REV. PLUGS and SOCKETS. P74 
2-pin 4/3; P73 3-pin 4/6; P194 6-pin 6/6; P486 12/6, 
RESISTORS' Preferred values. 10 ohms to 10 meg. 
i w., J w., 1 w., 20% 4d-; 1J w., 8d.; 2 w., 1/- 
HIGH STABILITY i w., 1% 2/-. All Values. 
10 ohms to 10 meg Ditto 5% 10 ohms to 22 meg., 8d. 
5watt-» 0.5 to 8.2 ohm 3 W r 1/6 

10 watt }• WTRE- WOUND RESISTORS J, 1/8 
15 watt J 10 ohms — 6,800 ohma L g/- 

10 K., 15 K., 25 K., 10 w. 8/- 

MAINS DROPPERS Midget. With sliders, 0.3a, 
1 K.. 0.2a.. 1.2 K., 0.15a., 1.5 K., 0.1a., 2 K-, 6/- 
each. Line Cord 100 ohms it., 3-way. 1/- ft. 
Wirewound Ext. Speaker Controls 10Q 3/-;'25Q 6/6. 
WIRE-WOUND POTS 3 WATT. Miniature TV 
Types. All values 10 ohms to 25 K.. 3/- each, 30 K., 
4/-. (Carbon 30 K to 2 meg., 3/-). All with knob. 
WIRE-WOUND POTS 4 WATTS. Long Jin. 8pindle. 
Value B0 ohms to 50 K-, 6/6; 100 K., 7/6. 
SPEAKER FRET Tygan various colours, 52ln. wide 
from 10/- ft.; 2Sln. wide from 5/- ft. 8amplos 8.A.E. 
EXPANDED METAL Gold or Silver 12 x 121n., 6/-. 

ARDENTE TRANSISTOR TRANSFORMERS 
D3036 7.3 CT.l Push-Pull to 3 ohms output 11/- 
D3034 1.5:1 C.T. Push-Pull Driver 11/. 

D3058 11.5:1 Output 3 ohms, 11/-; D1001, 12/- 
D239 4.5:1 Driver, 11/8; D240 8.5:1 Drivor, 11/6 
TRANSISTOR POTS 5 K Switched VC1545 5/3 

SUB-MIN EARPDZCE Xial or Magnetic 7/6 

SUB-MIN JACK AND PLUG 2.5 or 3.5mm. 8/6 pr. 



TV REMOTE CONTROL lor Philips 19TG111A. 
121A, 125A. 142A, 23TG111A, 118A, 121A, 131A. 
Cossor CT1910A. 21A, CT2310A, 21A. 31A. 
Stella ST1033A, 39A. 43A. 53A. Plug in with lilt. 
7-way cable, 3 DP switches, dual pot., volume and 
brightness. OA31 diode, etc. eto. List 3 gin. 
New boxed. OUR PRICE 12/6, post free. 



RETURN OF POST DESPATCH 

P. P. Charge 1/6 Full List It. C.O.D. 216 extra 



Blank Aluminium Chassis, 18 s.w.g.. 4 sides, riveted 
corners, lattice fixing holes, 2Jin. sides, 7 x 4in., 6/6; 
9 x 71n., 6/6; 11 x 7in., 7/6; 13 s 9ln., 9/6; 14 x llin., 
12/6; 15 x 1 tin.. 15/-; 11 x 3in., 6/6. 
Panels 18 s.w.g. 12 x 12in., 5/6; 14 x 3in., 4/6: 12 x 
Sin., 3/6; 10 x "in., 2/9; 6 x 6in., 2/-; 6 x 4in„ 1/6. 



RADIO COMPONENT SPECIALISTS 

Written guarantee with every purchai«UExporti-Sen*MfTiitMnoe-«iod postoge»=j»COJ34Buse»-133 r 68 p«s do«vS.R. Stn.S»lhurst 



337 WHITEHORSE ROAD 
WEST GROYDON /ho'ims 



1068 



PRACTICAL WIRELESS 



April. 1966 



8 tips 

for practical 
soldering 



\ 



\ 



4 



% 



\ 




NEW! 



The lnstani Has. 

SofderinQ Kit complete with 

tips, MttWMloM barrel, probe and solder. 

Complete £3 1t 6 

Atk for a demonstration from your local 

r or fill la too coupon below for full 

details. 




WBrVV 



»♦••_»•••«-••••« 



BURGESS 



SG 1225 KIT 



Address., 



1URIEM PPtbDOCTi CO, IT* 

SAPCOTE, UICWTER. 

Tel: Sspcote t9S Telex: 54541 



SLEEP LEARNING EQUIPMENT 

(as featured on Page No. 754 January issue) 
14 day Swiss movement Time switch — suitable for any tape 
recorder £4.5.0. P. &P. 5/- 

Under Pillow Speaker £1.7.6. P. & P. 2/fl 

Complete outfit including: Tape Recorder, time switch with 
microphone, underpillow spoaker and pre-recorded con- 
ditioning tape. £29.10.0. P. & P. 10/- 
Send S.A.E. for full details of the sleep learning method— 
the modern way to learn. 




P.W. REFLEX 2 
TRANSISTOR RECEIVER 

All components available tram R.C.S. 
2 King tuners, 6/6; Chassis and eyelets, 2/6 or 
Chassis with eyelets fitted, 3/8; Case, ready 
drilled with knob and dial, 4,'-; Perrite rod. 
lormer, wire and grommets, 3/6 or Aerial and 
tormer ready wound, 5/-; K.F. choke, lormer 
slug and wire, 3/-; All diodes and transistors, 
14/-; All resistora and condensers, oh: Deal aid 
earpiece and socket, 6/-. P. a P. 1/6. 



Mains POWER PACKS 

The Ideal economical and safe way of running any Transistor 
Radio, Record Player. Tape Recorder, Amplifier, etc. from 
A.C. Mains with complete safety. 



The MAJOR "Power 
Plus" for 9v.: 6v.: 4tv.: 
Single Output.P.&.P.2'6 
For 9v.+9v.; 6v.+6v.: 
4 * v . i 4. v . Two separate 
outputs. P. & P. 2/6 
Please state output* rn/uircu. 
All "Power Plus" unit* are com- 
pletely Isolated from mains by 
double wound transformer en- 
suring 100% safety. 



39/6 
42/6 

required. 



The BIJOU "Power 
Plus". For the smaller 
set using PP3 type 
battery. Supplied com- 

Elete with special adap- 
jr enabling you to 
reactivate your existing 
PP3 type bat- -jy Ig 



tery. 



P. ft P. 2/6. 



R.C.S. PRODUCTS (RADIO) LTD. 

II Oliver Rd., London, E. 17. (Mail Order only) 

_______ Export Trade Enquiries Invited ________ 



GUITAR AMPLIFIERS 
With TREMOLO 



IS months' raaraa-a (takes 8 month!) 



*____. 



Five lack tnrX- 
et Inputs with 
four separate 
mixing volume 
controls. High 
gain of 10 milli- 
volts makes It 
suitable tor all 
typos ot guitars 
and micro- 
phonej. Sepa- 
rate Bsm and 
Treble controls. 
Master gain 
control. Trem- 
olo speed and 
depth controls. 
Bemote trem- 
olo switch sock- 
et. 7.6 and IE 
ohms outputs. 
SO and 60 
watt valves 

ECC8S, ECC83. BL34. BM4. OZ84. 16 watt Valvw. ECC83, ECC83. 

EL8-4, ELS4, EZ81. Two extra valves ECCS3 used in the tremolo circuit. 

Tremolo operates on one Input only. Black and gold front panel cat'.cd 

tremolo type only at present) Chassis finished silver grey hammer. Cover 

with chrome bandies 35/- extra. 

PRICES 

60 watt with tremolo .,..£21.17.6 

60 watt less tremolo . . . .119.10.0 

SO watt with tremolo . . . .£16.17.6 

80 watt lets tremolo . . . ,f 14.10.0 

16 watt with tremolo . . . .£13.17.8 

16 watt less tremolo . , . .111-10.0 

Add carriage 10/- any amplifier. Credit terms arranged. Descriptive 

leaflet tnt, stamp appreciated. Suitable speakers. Bikers 12* Guitar LB. 




STOP PRESS: 

100 watt with tremolo 

100 watt leas tremolo 



SSS.17.S 

SS4.10.0 



5 gns. Bakers 15' Group 60 1.8. 18 gal. Carriage tree. 



Cash with order only, regret no C.O.D. 



"No trade or export" 



STROUD AUDIO 

CASHES GREEK BOAS, STROUD, 6W* STROUD 783. 



April, 1966 



PRACTICAL WIRELESS 



1069 



(5) Again check for continuity but this time 
across the movement lead-in connections, i.e. 
close to the hairspring. If no reading is 
obtained check, using a lens, for broken 
connections. If there are no breaks the coil 
is damaged beyond amateur repair. 

(6) If a reading is obtained when the movement 
is checked at the lead-in connections look for 
a minute break at the termination of a small 
coil on top of a resistor attached to one input 
terminal. (The break is probably caused by 
wire, hardened by age and subjected to 
fairly severe vibration during service life.) 
Resolder the connection and check the meter 
from the external terminals. 

(7) Remove the existing dial. Prepare a new dial 
numbered one to ten and attach it to the 
existing dial (as was done with the band- 
spreader dial). Refit the modified, dial to the 
meter. 

(8) Reassemble the meter and put it aside mean- 
time. 

(9) Cut all wiring to the monitor switch. Remove 
the switch. 

(10) Fit a nine-way single-pole switch in place of 
the removed monitor switch. (Space is limi- 
ted, therefore the diameter of the new switch 
must not exceed ljin..) 

(11) Obtain about 15in. (at least) of nine-way 
multicore cable, preferably having leads of 
different colours. Strip the outer sleeve (and 
screen if any), then prepare iin. tinned 
connections at one end of the cable. Pass 
the untreated tail of the cable through one 
of the two eyeletted holes adjacent to the 
bandspread capacitor. 

(12) Turn the monitor switch knob fully counter- 
clockwise and locate contact 1. also the 
wiper contact. To contact 1 solder one 
tinned lead of the cable. Follow on with the 
remainder, of the cableform, noting on a 
monitor schedule the colour of each lead 
and its relevant contact on the monitor 
switch. 

(13) When all leads have been attached to the 
switch contacts solder a 3in. lead to the 
switch wiper. 

(14) Refit the meter. Earth the negative terminal. 
To the positive terminal connect the -switch 
wiper lead. 

The selection of monitored points is, perhaps, 
something for the reader to decide since views on 
this subject are many. The author suggests the 
following as being very useful (reasons are given 
against the less obvious points): 

(1) Main h.t. at rectifier cathode. 

(2) Main h.t. at choke output. If a fault changes 
the h.t. current demand noticeably this is 
shown by a change in the known difference 
between the cathode voltage and the correct 
value of choke output voltage. 

(3) Automatic volume control (measured by its 
effect on cathode bias of VIC. This setting 
provides visual tuning control and indication 
of signal amplitude but only on R.T.). 

(4) Beat-frequency oscillator cathode bias. (If no 
b.f.o. note can be obtained this setting pro- 
vides a quick check on (a) the presence of h.t. 



at the valve, (b) whether or not the valve is 
oscillating. In case (a) there is no bias reading, 
in case (b) the reading is above normal.) 

(5) Frequency-changer bias. (If the oscillator 
section of the 6K8 fails the bias reading is 
slightly, but noticeably, greater than when the 
oscillator is normal. Two conditions are noted 
in the monitor schedule: (a) Normal 
operation at 4-5Mc/s, (b) bias with the 
oscillator dead.) 

(6) Frequency-changer oscillator h.t. 

(7) First a.f. amplifier cathode bias. 

(8) Output stage cathode bias. 

(9) In the author's receiver this position is used 
to monitor the 4- 28V supply to a teleprinter 
used in conjunction with the receiver. 

All of the above are shown in Fig. 6. Whichever 
circuits are chosen the value of resistor to be 
connected between the monitor point and the 
cableform lead can be found from the Ohm's Law 
formula : 

R=E/I where R is in megohms, E in volts, 
and I is a fixed value, 250 (this is the half- 
scale reading of the monitor meter). 

For example, supposing one wants to monitor a 
10V cathode bias point, 

R= 10/250 = 004Mn=40kn. 

Since the readings need not necessarily be 
exactly half-scale any value between (say) 37kfl 
and 44kfl should be satisfactory. 

Two points which should have the same resistor 
value, however, are the rectifier cathode h.t. and 
the choke output h.t., the. reason being that one 
requires a comparison of meter readings to show 
the voltage drop across the resistor in the h.t. 
supply. 

When all wiring has been completed in the 
monitoring system the cableform should be laced 
with buttpn thread to tidy off. The receiver 
should then be run up and" allowed ten minutes or 
so for temperature stabilisation, then the various 
readings taken down on the monitor schedule, 
which should be attached to the receiver, or filed 
for reference. 

The inclusion of a monitoring system completes 
the series of modifications carried out by the 
author. If no snags have been encountered and 
the original receiver was in reasonable condition 
to begin with the reader should now possess a 
receiver whose performance in the 2 to 8Mc/s 
band is the equal of many very much more 
expensive receivers. If he has had experience in 
alignment of receivers he may be able to improve 
this high performance still further by slight 
co-ordinated adjustment of the four compression 
trimmers situated in the area to the rear of the 
waveband switch. (The fifth trimmer, near the 
panel, alters beat frequency and should be left 
alone.) If he has no realignment experience leave 
these four trimmers to someone with the necessary 
knowledge to adjust them. 

Ensure all superfluous wiring and wire clippings 
are cleared out of the chassis and that new wiring, 
components, etc., will be clear of the inner base 
when fitted. Drill the outer case to pass the mains 
cable (and provide access to the mains fuse if 
fitted), then fit the receiver into its outer case to 
complete the job. ■ 



+250V 



MIC PREAMP 



A high-gain unit using 
a single transistor 

by A. E. J. Simons 



Preamplifier Performance 250V H.T. 

Voltage gain 320 

Current consumption 0-7mA 

Output impedance 5kSl 

Input impedance .................. 200J1 




Existing amplifier input stage 



Fig. 2: The arrangement of a valve amplifier input stage 

for connection of the preamp. R has a value to regulate the 

amplifier h.t. to 250V for the preamp. C=fyiF 350V. 



THIS high-gain preamplifier is suitable for use 
with a succeeding valve amplifier. The normal 
250V h.t line will supply the requirements of 
the OC70 Mullard transistor via resistors R4 and 
R5. Having no hum or microphony and a voltage 
gain of over 300 the preamplifier is suitable for a 
low-impedance microphone or pick-up. 



a Ri 
cA— WWW 

Input 




.4— ID— :: 



R5 +ve 
■VWVW 25QV 

Fig. 1 1 The single-transistor circuit of the unit. 

The writer has used the preamplifier as a second 
microphone input to an existing valve amplifier 
with excellent results. The output of the pre- 
amplifier was connected to the gramophone 
pick-up sockets; the gramophone volume control 
thus became the second microphone gain control. 
Being only 3in. x Hin. x iin. in size, the unit fits 
easily into a tape recorder, care being taken to 
keep the transistor away from components which 
run hot, i.e. valves and smoothing resistors. 



RI 

R2 
R.3 
R4 
R5 


COMPONENTS LIST 

100ft CI IOOuF 12V 
lOOkQ C2 0-lpF 150V 
470kft Trl Mullard OC70 
5-6kft 
330kO 
All resistors ±W 5% high-stability. 




Notes: 
Output lead V should 
be screened It It 
exceeds 6 In length 

The transistor should 
be connected after 
all other components 
have been mounted 
and wired up 

Fig. 3: Construction of the unit is on a piece ofpaxolin and 
the above layout was used successfully by the author. 



Construction 

The preamplifier can be built on a paxolin strip 
3in. x l$in. The strip should be drilled to take 
the wire ends of the components, which are twisted 
together behind the strip and soldered — shown by 
heavy dots in Fig. 3. Input, h.t. and output 
connections are made with flying leads. 

Before connecting to the h.t supply check the 
polarity of the preamplifier. Successful operation 
has been obtained with an h.t supply of between 
1 50-260 V. Should the valve amplifier h.t. be in 
excess of 260V it can be reduced to a safe level 
as shown in Fig. 2. This also shows the method 
of coupling the preamplifier to the valve 
amplifier. 



April, 1966 



PRACTICAL WIRELESS 



1071 



Exclusive to Practical Wireless Readers 



PRIVILEGE PRICE 
BOOK OFFER 



PRACTICAL WIRELESS 

Radio and 
Television 
Reference 



Data 



COMPILED BY 

J. P. HAWKER 




Packed with practical data covering the whole field of 
radio and television, this invaluable book provides an essential 
reference source for every amateur constructor and experimenter. 
Take this unique opportunity now of obtaining this reference 
book at the privilege price offer of 5/- (value 10/6). 

96 PAGES of Factual Tabulated Data, with sections on:- 

Colour Codes - Formulae - Aerials • Frequency and Wave- 
length ■ Broadcasting Allocations ■ Station Frequencies. 
Television Standards - Symbols; Abbreviations - Amateur 
Radio - Useful Constants - Amateur Radio Prefixes - I.F. 
List for Communications - Receivers - Mathematical 
Data • Wire and Cable Data • Valve, Picture-Tube, 
Battery and Transistor Data. 



TO ORDER Please complete 
the coupon, using block capitals, 
and enclose remittance tor 5/- 
(Cheques and Postal Orders should be 
made payable to George Newnes 
Limited, and crossed.). Name and 
address must be written on back oi 
cheques. Send your order to: 
PRACTICAL WIRELESS BOOK 
OFFER, Carlton House, Great Queen 
Street, W.C.99. Closing data 30th 
April, 1966. We regret that this offer is 
not available to Eire and Overseas. 



ACT 
NOW! 
SEND 
THIS 
FORM 
TODAY! 






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NAM 


F 


APRIL 1966 


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1 IF UNDELIVERED PLEASE RETURN TO GEORGE NEWNES LTD., 1 
| 136 LONG ACRE, LONDON, W.C.2. | 



1072 



PRACTICAL WIRELESS 



April, 1966 







"^ STEREO 

AMPLIFIER ASSEMBLY 




F.M. TUNER 



# 5 stage input Selector £2.7.6 

9 Pre-amp. and vol. control £1.17.6 
9 Pro-amp. with tone controls £3.2.6 
Send for leaflet describing entire range 



mfl RTin 



O 10 watt amp. (3 ohms) £5.12.6 
10 watt amp. (15 ohms) £6.12.6 
*) Mains power supply £2.15.0 



KITS WITH A FUTURE 

The Martin Audiokit assembly you own today can 
become part of an even better hi-fi system tomorrow. 
No other system allows you to enlarge your 
installation stage by stage in the way Audiokits do. 
They comprise a wide range of very well made 
prefabricated units in which the connections are 
standardised throughout. Each is rigorously tested to stated 
specification before despatch. NEW KITS FOR 
ADDING ON ARE IN COURSE OF PREPARATION 
NOW — so by starting with Martin today, you insure 
yourself for still better listening tomorrow. 

Choose Martin for quality 

% Build for 3 or 15 ohm system 

# Start with Mono and add Stereo or start 

completely with Stereo 
% Power packs available 
% Professionally styled escutcheon plates 

Assembly is easy by following the well 

presented instructions. 



Martin Audiokits and Hecordakits 
are obtainable from good stockists 
everywhere. In cases of difficulty 
please write direct. 



MARTIN ELECTRONICS LTD. 154-155 High Street 

Brentford Middlesex 
Full details of Martin Audiokits please 



NAME. 



ADDRESS 



MARTIN ELECTRONICS LTD., 154/155 HIGH ST., 

Phone: ISLeworth 1 161/2 



BRENTFORD, M'SEX 



(Block letters) 



PW.4 



TWO-YEAR GUARANTEED TUBES 



14 in. 



17 in. 



21 in. 

and all 
Slimline 
Tubes 




100% REG UN NED 
Add 10'- or old tube. 
1 1 0° — 30'- on old tube. 
Carr. I0'6. I4in. Slim- 
line 17 & 19 in. — 
overseas postage 30'-. 



EX-MAINTENANCE TESTED TUBES 

I7in. — 35/- Most makes and types available. I4in. — 15/- 
Guaranteed good picture. Carriage 5'- extra. 



EX-RENTAL 

TELEVISIONS 

14 In. 17 in. 

£7.10.0 £11.10.0 

12 months' 3 star Guarantee 

■^■Tube-^Valves-^ Components 
COLOURED FREE LIST 
Channels for all areas 

Oemoatxra tions daily from Large 

Selection. 

Personal collection or Insured 

Carr. I4in. 20'-; I7in. 30'-. 




TWO-YEAR GUARANTEE 

On all our slimline TV's send for free list. 



Record player 
cabinets 49'6. 
Latest design 
covered cabinet 
takes any mod- 
ern autochanger. 
Single player 
cabinets I9'«. 
P. * P. 5/4. 



VALVES £1 per 100. Assorted TV and Radio. 

Surplus ex-rental dismantled receive™. Post 4/6. 

8end for list. 

CONDENSERS, 10/- per 100. New Assorted Eleetro- 

Ivtics and pi's. P. * P. 2/6. 

RESISTORS, 6/- per 100. New, Mostly Higb Btabe. 

Assorted. P. 4 P. 2/-. Overseas 3/6. 

SPEAKERS, 7/9, 61n., Sin., 7 x 4m,. 8 X Sin. Ex-mfd. 

Salvage. P. & P. 2/3. Overseas, 4/-. 

DUKE&CO.(LONDON)LTD. 

421/3 Romford Road, Manor Park, E.I2 

Liverpool St. — Manor Pk. — 10 mins. 

Phone: ILFord 600-1-2-3. Sump for Free List. 




For quick, easy 
faultless 
soldering 



Ersin Multicore 5-core solder is easy to use and eco- 
nomical. It contains 5 cores of non-corrosive flux, 
cleaning instantly heavily oxidised surfaces. No extra 
flux is required. Ersin Multicore Savbit Alloy 
considerably reduces the wear of copper soldering 
iron bits. 




HANDY SOLDER 

DISPENSER 

12 ft. -of 18 s.w.g. 
SAVBIT aUoy in a 
continuous coil, used 

direct from free- 
standing dispenser. 

2/6 each 




LOW TEMPERATURE 
SOLDER 

Size 9 pack contains 

24 ft. of 60/40 high 

tin quality 22 s.w.g. 

2/6 eaob 
Size 10 pack 212 ft. 
Ijl- each. 




SAVBIT 

SIZE 1 CARTON 

Contains approx. 30 ft. 

of 18 s.w.g. SAVBIT 
alloy. Also available 
in 14 and 16 s.w.g. 

5/- each 




BIB WIRE 
STRIPPER 
AND CUTTER 

Strips insulation, 

cuts wire cleanly. 

Adjusts to. any size. 

4/- each 



Available from all Electrical and Hardware shops. 
If unobtainable write to: 

MULTICORE SOLDERS LTD. 

Midticorc Works, HemelHempstead,Hen8.HcmelHempstead3636 



An 

ELECTRONIC 
GATE 

or 

TRACE DOUBLER 




FOR SINGLE BEAM OSCILLOSCOPES 



H. T. Kitchen 



THE majority of oscilloscopes used by the 
majority of amateurs have one characteristic 
in common, the inability of displaying two 
separate signals as two separate and distinct 
waveforms on their cathode ray tubes at the same 
time. They are, in other words, single beam 
oscilloscopes. 

Now it is quite probable that many amateurs 
will never need, or want to, view two different 
signals simultaneously, whilst others, like myself, 
will only need to do so from time to time. 
Undoubtedly the easiest way of doing so is by 
using a double beam oscilloscope, though this type 
of instrument, due to its high cost, can almost 
certainly be regarded as an unjustifiable luxury in 
all but a few exceptional cases. We must not, 
however, overlook the amateur who has either 
bought or constructed a first-class single beam 
oscilloscope for, having spent a goodly portion of 
his hard-earned income upon it. he will not exactly 
be overjoyed at having to start again. 

Fortunately it is not unduly difficult to obtain 



Oi 



lT 




m 



MLJ1. 



double beam operation from a single beam 
oscilloscope, though not, unhappily, with the same 
facility as would be obtained from a genuine 
double beam instrument. This is brought about 
by the use of a special electronic gate into which 
the two signals are fed simultaneously. The gate 
then allows each signal to be passed turnabout to 
the oscilloscope, suppressing in the meantime the 
signal that is not being passed, the net result being 
two separate waveforms corresponding to the two 
separate signals. 

Gate Principles 

The principle of the electronic gate is quite 
simple and is illustrated in Fig. I. It comprises 
two amplifiers for the Yl and Y2 signals and a 
gate generator which provides two gating signals, 
these being square waves of identical frequency 
but out of phase by 180°. These are also fed into 
the Yl and Y2 amplifiers and alternately allow 
them to conduct and then drive them into cut-off. 




Fig. I : Diagram showing operation of the electronic gate. 



Fig. 2: The effect of a slow gating speed. The YI-Y2 wave- 
forms are composed of positive and negative peaks of the 
gating waveform. 



1074 



FRACTICAL WIRELESS 



April, 1966 



Being in anti-phase it follows that when the Yl 
amplifier is conducting, the Y2 will be cut off and 
vice versa, so that the c.r.t. is presented with a 
sequence of " samples " which, if the gating 
waveform is of the correct frequency, gives the 
impression of two separate traces. If the oscillos- 
cope timebase is adjusted to display the gating 
waveform the Yl and Y2 signals will be seen to 
occupy the horizontal portions of the square waves' 
positive and negative peaks. This effect, which is 
shown in Fig. 1 and also in Fig. 2, is only 
shown to explain how the gating waveform 
provides two separate traces. In actual use the 
timebase will be used to display the input signals 
only and the gating waveform will not be visible 
except under certain circumstances. These will 
ooour when a fairly slow gating speed is used and 
the input signals will be seen to consist of a series 
of dots or dashes, depending on actual frequency, 
which are really the positive and negative peaks 
of the gating waveform. At high gating speeds it 
is possible for the intervening spaces to be 
rendered luminous by the gating waveform and 
occasionally for the waveform to be faintly 
discernible. With practice it is possible to ignore 
both effeots and concentrate only on the wave- 
forms to be examined. 

With a double beam oscilloscope each trace has 
its own vertical shift control and so can be 
positioned just where it is wanted. The two traces 
can be superimposed, transposed or one removed 
right off the screen. With an electronic gate, 
however, the two traces will move as one every 
time the oscilloscope's vertical shift control is 
operated. The superimposition and transposition 
facilities can, however, be retained, though neither 
trace can be removed off the screen without going 
to some, and usually unnecessary, trouble anyway. 
The gating waveform, as already explained, is a 
square wave which is fed into the two amplifiers 
out of phase by 180°. If the gains of the two 
amplifiers are exactly equal the two anti-phase 
signals will cancel out and in the absence of any 
Yl or Y2 signals will show on the oscilloscope as 
a straight line. Where Yl and Y2 signals are 
present they will be superimposed, occupying, as 
they do, a common baseline. Although this may 
suffice for some applications it is an unsatisfactory 
way of doing things, for there is every possibility 
of the superimposed traces causing misunder- 
standings and mistakes. It is desirable to either 
separate the two traces so that they are no longer 
superimposed or else to make one much brighter 
than the other or even to make the best of both 
worlds by combining them and neither objective is 
particularly difficult to achieve. 

It was earlier stated that if the two Y amplifiers 
had equal gains the gating square wave would 
cancel out and the oscilloscope would simply 
display a straight line. It must be understood that 
since both the gating and the external signals are 
fed into the Y amplifiers this remark will apply to 
tihc gating waveform's gain only and not to the 
»gnal gain. If the gain of the two amplifiers to 
the gating waveform is made unequal the output 
will be a square wave and it will be possible to 
separate the two external signals. This is done 
most easily and conveniently by varying the bias 



SPECIFICATION 
Power Supply Required: 

250V at 20mA 
6-3V C.T. at I -2A 
Y Amplifiers: 

Freq. Response: I5c/s— 50kc/s ±ldB 
lOc/s— 200kc/s ±3dB 
Input Impedance: I Mil 
Gain : x5 

Gate Generator: 

Fixed frequencies of SOc/s, I75c/s, 500c/s, I750c/s, 
SOOOc/s approx. 
Gate Output: 85V P-P (anodes of VI) 

Gating Transients: I IV P-P (cathodes of V2 V2) 

Note I 

All static voltages except multi: VI measured 
with VRI at mid position and with SI at "off" 
position using 250V and 10V ranges of 20k£2/V 
meter. 

Note 2 

Gain and frequency response of Yl Y2 amps 
measured separately with VRI at mid position 
and gate at "off". 



on the gating stages, so causing unequal anode 
currents to flow in the common anode load 
resistor, thereby providing the required unequal 
outputs. It is customary to label the top trace the 
Yl and the lower the Y2 trace and to label the 
input sockets accordingly, thereby making it 
possible to identify the two signals. 

It is also possible to make one trace more or 
less brilliant than the other by varying the mark 
space ratio of the gating square wave. The two 
traces will be equally brilliant when the gating 
waveform has a mark space ratio of one to one. 
If the mark space ratio is altered the two traces 
will differ in brilliance since one waveform, the 
more brilliant of the two, will be allowed to 
remain longer on the cathode ray tube than the 
dimmer trace which will have been allowed the 
least time. In practice the mark space ratio can 
be altered by providing the multivibrator with 
unequal grid leak resistors or by making the cross- 
coupling capacitors unequel in value. It is not 
usually possible to alter the mark space ratio to 
any great extent without adversely affecting the 
waveform. 

Although an electronic gate will provide the 
services of a double beam oscilloscope it is by no 
means a perfect substitute for one since it suffers 
from a number of inherent disadvantages which 
limit its scope (no pun intended!) and usefulness. 
It is proposed to explain these disadvantages in 
some detail in order that the reader will be in a 
position to judge whether or not the gate will be of 
any use for his own particular applications. 

Limitations 

Strangely enough one of the limitations is the 
oscilloscope into which the output from the gate 
will be fed. This output will consist of the two 
external Yl and Y2 signals plus the gating square 
wave which has been described, with perhaps some 
justification, as the carrier wave. Now one of the 
properties of a square wave is its ability (unwanted 



April, 1966 



PRACTICAL WIRELESS 



1075 



LEARN 

ELECTRONICS 

-AS YOU BUILD 



over 



including . . . 




CIRCUITS 
EXPERIMENTS 
TEST GEAR 



CATHODE RAY OSCILLOSCOPE 




Valve Experiments 
Transistor Experiments 
Electro-magnetic Experiments 
Basic Amplifier 
Basic Oscillator 
Basic Rectifier 
Signal Tracer 
Simple Counter 
Time Delay Circuit 



Square Wave Generator 
Morse Code Oscillator 
Simple Transmitter 
Electronic Switch 
Photo-electric Circuit 
Basic Computer Circuit 
Basic Radio Receiver 
A.C. Experiments 
D.C. Experiments 



The full equipment supplied comprises valves, transistors, photo-tube, modern type chassis board, printed circuit board, full rang* 
resistor:, capacitors and inductors, transformers, potentiometers, switches, transistors, valves, all hardware, wiring and every detail 
required for all practical work plus CATHODE RAY OSCILLOSCOPE for demonstrating results of all experiments carried out. All practical 
work fully described in comprehensive PRACTICAL MANUALS. Tutor service and advice if needed. 



This complete practical course will teach you al. the basic principles of electronics by carrying out 
experiments and building operational apparatus. You will learn how to recognise and handle all 
types of modern components; their symbols and how to read a completed circuit or schematic diagram. 
The course then shows how all the basic electronic circuits are constructed and used, and HOW THEY 
ACTUALLY WORK BY USING THE OSCILLOSCOPE PROVIDED. An application Is given In all the main fields of 
electronics, i.e. Radio; contro 1 circuits; computors and automation; photoelectrics; counters, etc., and 
rules and procedure for fault finding and servicing of all types of electronic equipment. 



NO PREVIOUS KNOWLEDGE NEEDED 
SENT IN ATTRACTIVE BOX 



• NO MATHS USED OR NEEDEO 
W COMPLETE ADVICE SERVICE 



REASONABLE FEE— NO EXTRAS REQUIRED 
EVERYTHING REMAINS YOUR OWN PROPERTY 



A completely NEW up-to-date 
home study experimental 
course by 

BRITISH NATIONAL 
RADIO SCHOOL - 
Britain's Leading Electronic 
Training Organisation. 



r 

I 



POST NOW FOR FREE BROCHURE 



To BRITISH NATIONAL RADIO SCHOOL, READIN6. BERKSHIRE Please send 
free Brochure, without obligation, to 



ADDRESS 



Block Capitals Please 
Ol WRITE IF YOU PREFER NOT TO CUT COUPON 



1076 



PRACTICAL WIRELESS 



April, 1966 



BRAND NEW AM/FM (V.H.F.) RADIO 
GRAM CHASSIS AT £15.15.0 (Carriage Paid) 




Chassis _• IS r 8J x 6 Jin. high. New manufacture -Dial 14J x *in. in 2 
colours, predominantly cream. 200-260V. A.C. only. 

Pick-up. Ext. Spcakei. Ae., B M and DIpole Sockets. Five push-buttons — 
LW, MW". SW, EM and Gram. Aligned and tested. O.P. Ti-nnsformer 
Tone control. 1000-1900 M.; 200-550 M-; 88-98 Mc/s. 6-17 mc/s. EZ80 rect.; 
ECH81, EF89, BAB080, EL84. ECC85. 3-ohm speaker required. 
9 i 6ln. ELLIPTICAL 8PEAKER. 20/- to purchasers of this chassis. 
TERMS: (Chassis), 23.10.0 down and 6 monthly payments of £8.4.0. Cheap 
Boom DIpole for V.H.P., 12/6. Feeder Sd per yard. Total HUP. price El 6.14.0 
Circuit diagram 2/6. Carriage to N. Ireland 20/- extra. 

HEW 6 PUSH-BUTTOK STEREOGRAM CHASSIS M.W.; B.W.I: 8.W.2; 
V.H.F.; Gram; Stereo Gram. Two separate channels for Stereo Cram with 
balance control. Also operates with two speakers on Radio. Chassis size: 
15 x 7 i 6Jin. high. Dial cream and red. 15 x 3in. Valves ECC35. ECH81, 
BF89, 2 x ECL86, EM84 and Silicon Rect. Price £17.17.0, carr. paid 
or £4.0.0, deposit and 6 monthly payments of 50/-. Total BuP. price 
£19.0.0. Cream moulded escutcheon for dial, 7/6 extra. 

BATTERY ELIMINATOR 

For 4 tow consumption valves (96 range) 90v. 15mA and 1.4v. 125 mA, 42/6 
(4/- post), 200-250T. A.C. Also for 250mA, L4t. and 90v. 16mA at same 
pries. Two units each St i 31 i If In. 




ffULP-POWKEED VHP TONER CHASSIS 
Covering 88-95 Mc/s. Dims. 8 x 6 x 6m. 
high. Valve* EOC86. EABO80 and 
2-EF89's with metal rectifier. Mams 
transformer. Fully wired and tested 
ONLY £8.17.6 <carr. paid). Room 
drpole, IB/6. Feeder Sd. per yard. 




SUPER 6 

LONG & MEDIUM WAVE 
TRANSISTOR RADIO ■ 

A quality radio available as a kit or ready-built. The sparkling performance 
and superb finish of the completed receiver give you value equivalent to a 
412.12.0 commercial model. 

■*■ All new ports, -fc 6 transistors and dlodo. -jV 350mW output, -jlr Superhet 
circuit. •*• Ferrlte rod aerial. * Weymouth Radio printed circuit board. 
■*• Component positions and references printed on back of board. + Nicely 
styled wooden cabinet, 11 x 7i x 3iin- * Vinyl covered in various colours. 
■*• 6 x 4in- speaker giving good bass and treble response, ir Full instruction 
booklet, 2/-. Free with kit. * I-F. Ircquency 470 ke/s. ■*■ Lining up 
service if required, -fr All parts supplied separately. Write for Ust, 8.A.E. 
PLCS 5/- POST. COMPLETE KIT ONLY £4 
OB FVLLT BUILT £6.7.6. Tax & Oarr. Paid 

8 WATT PUSH-PULL O.P. AMPLIFIER 
£5.5.0 (6/- Carr.) 

200-240 A.C. mains. Bass, treble 
and vol. controls. EZSO, ECC83 
and 2-EL84 - «. Chassis 12 x 3» x 
8$in. With o.p- trans, for 2-3 ohm 
speaker. Front panel (normally 
screwed to chassis) may be removed 
and used as flying panel. With 
Cream/Black control panel whole 
length of front chassis. 




GLADSTONE RADIO 

66 ELMS ROAD, ALDERSHOT, Hants. 



! rains, from Station and Buse?)._ 



>«>«»**•*« 



CLOSED WEDNESDAY AFTERNOON 

CATALOGUE 6d. 
Regret overseas orders cannot be executed 



Aldershot 22240 



100 WATT AMPLIFIER AND 

8PEAKER SYSTEM FOR 

COMPLETki GROUP 

* Separate High and Low frequency channels of 
60 watts each. Each channel having 4 jack-inputs 
with 2 volume controls plus bass and treble controls. 

* Amplifier unit contains 12 valves, 6 per channel 
In four gain stages with pre-amp and push-pull 
output. 20mV sensitivity, frequency response 
30-20,000 o/s. Hum level -70dB. 

* Two speaker columns each with 3 x 12m. speakers 
for High frequency and a bass cabinet housing 
4 x i*>1t>, speakers for Low frequency. RA and 
Fane speakers used with total rating 140 watt*. 

* Housed In four acoustically designed and styled 
covered cabinets. 

_ ~S 

Carr. Free 

* A really Hi-Fi de luxe system with tremolo on 
HI channel, using all Goodman speakers is available 

1 K_ GNS. 
at IOW Carr. Free 

WE ALSO OFFER 
FULLY TRANSISTORISED 

All units self contained with 9V battery. Carr. Free. 

PRE-AMP— 49/6 

Variable high gain unit with single Jack input. Jack 
output suitable for guitars, microphones, gram, 
tape, etc 

MIXER-UNIT/PRE-AMP-115/6 

Four jack Inputs, single Jack output using five 
transistors with four independent volume controls, 
suitable for many application*. The Ultimate xor 
group microphone mixing. 

TREMOLO UNIT— 84/6 

Two Jack inputs, having speed, volume and depth 
controls with provision for foot-switch operation. 

D.A.B. Electronic Consultants 

2 Albany Road, Holbury, Southampton. 




ThtWUMCH 

uou need! 



HOLE PUNCHES 
Instant Typo 

|" diameter 

Screw-up Type 

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2&" 



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IS' 1 „ 

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Complete Set 9.3.6. 

No extra charge for postage and packing 

in the U.K. 

Now supplied by 

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237 GIPSY ROAD 
WEST NORWOOD, S.E.27 

Ttl. Gipsy Hill SOW 



4 STATION INTERCOM 




tlon probloi 

new 4-Station Transistor Intercom II master and 
8 Subs), in de-luxe plastic cabinets for desk or wall 
mounting. G_/_k/— ten from Master to Subs and 
Subs to Master. Operates en one 9V battery. On/ofl 
■witch. Volume control. Complete with 3 connecting 
wires, each 00ft. and other accessories. P. 4 F- 4/0. 



INTERCOM/BABY ALARM 



Usually -&Gfi§r 
OtrfMaONLY 

57'6 



Modernize business or home with this now two-way 
Transistor Intercom, consisting o' Master and Sub, 
in strong plastic cabinets, with chromium stands. 
Designed as a two-way instant communication 
system — call/talk/listen. Operates on one 9V battery. 
Complete with 00 ft. wire. Battery 2/8. P. & P. 2/6. 

69/6 

Why not 
boost bus 
iness, effi- 



mmmmih 




Telephone Amplifier with Rotary Calenda 
Holder. Take down long telephone messages or con- 
verse without holding the handset. A status symbol? 
Yes, but very useful one. Ou/oH switch. Volume Con- 
trol. Operate" on one 9V battery (supplied). P. & P. 
8/8. Pull money refunded If not satislied in 7 days. 

WEST LONDON DIRECT SUPPLIES <PW/11.> 
6 CHIGNELL PLACE, WEST EALING. LONDON W13 



April. 1966 



PRACTICAL WIRELESS 



1077 



in this particular application) to reveal the charac- 
teristics of the equ.pment through which it has 
been passed. Sagg.ng or slop.ng tops will denote 
a phase advance due to a poor low-frequency 
response, whereas rounded corners w,ll denote a 
phase lag caused by a poor high-frequency 
response. In really bad cases the emergent wave- 
form will bear very little resemblance to the 
ingoing one. It will therefore be evident that for 
successful operation of the gate the oscilloscope's Y 
amplifier must pass the gating square wave w.thout 
distorting it, at least to any excessive extent. If it 
is unable to do so the output from the gate will 
have to be fed directly to the cathode ray tube's Yl 
plate, in which case some alteration to the deflec- 
tion circuitry will probably be necessary. Where 
the oscilloscope's vertical amplifier uses symmet- 
rical or push-pull deflection it will be necessary to 
earth the Y2 plate (capacitively if there is any z.f. 
voltage on it) and to feed the gate to the Yl plate 
only. Due to the variety of deflection circuits in 
common use more explicit directions cannot be 
given, though it can be said that additional 
amplification before and after the gate will 
probably be necessary and will be due to the very 
small gain afforded by the Yl and Y2 amplifiers 
plus thei- inability to deliver the very high peak-to- 
peak voltages necessary to fill the working area 
of the c.r.t.. It must be emphasised that these 
modifications will only be necessary with very 
simple oscilloscopes with restricted vertical band- 
widths and it is quite possible for the gate to work, 
at least reasonably well, with the majority of 
amateur oscilloscopes. It is safe to say that if the 
oscilloscope can reproduce the gating square wave 
with reasonably vertical sides, square shoulders 
and reasonably horizontal positive and negative 



peaks that it will work well with the gate. 

Yet another limitation is the gat.ng speed. In 
theory it should be naif the t.mebase spe;d so that 
each waveform can be traced out in turn. In 
practice surprisingly good results can be obtained 
with very widely varying gating/ timebase speeds. 
Some authorities recommend a low ga.ing speed, 
others a high speed. My own experience is mat 
very slow gating speeds cause the waveform to 
sparkle in a rather fascinating way which causes 
eyestrain rather more rapidly, whilst very high 
gating speeds cause the space between the Yl and 
Y2 waveforms, to be rendered luminous. Of the 
two the latter effect is preferable to the slow speed 
sparkling, but since individual preferences vary 
and since it Is desirable to work at half the time- 
base speed whenever possible the gating waveform 
is made variable in frequency. 

Bandwidth 

The last disadvantage to be covered is that of 
bandwidth. By the very nature of its operation 
the bandwidth that can be covered is restricted to 
the audio and low radio frequencies and is due to 
the inability of the simple gating circuit used to 
generate rhe ideal square wave necessary to bring 
about satisfactory gating at high frequencies. It 
will nevertheless satisfactorily handle 200kc/s 
since waves as shown in the waveform diagrams 
for which purpose the two inputs were temporarily 
connected in parallel. The distortion evident was 
present in the input signal which was derived from 
a transistorised " Nombrex " signal generator. 
This shows that in spite of the remarks concerning 
the recommended gating to timebase speed ratio 
of 2-1 (or 1-2) acceptable results can be obtained 





i^svy 



*m 4 rTMr 



assS «* 3 u7 



^±U^f 




AH resistors are >SW«tt 20% tolerance 

except wnere otherwise stated. 

R1.R2.R3 .R4.R6 and R9 are 

Vh tolerance. 

CapacitorsCl toC4 *ndC6 toC» 

are 2'h tolerance. 

C13.C14.C'7,C16 and C19 

are 3SOV working. 



Fig . 3: Complete circuit of the trace doubler. 



1078 



PRACTICAL WIRELESS 



April, 1966 



with widely differing ratios, for the gating speed 
used in this case was l,750c/s. Although my own 
tests ceased at 200kc/s it is not unreasonable to 
suppose that even higher frequencies could be 
handled, though the signal gain would be well 
down when compared to the reference frequency 
of lk/c. These remarks apply to sinewaves, the 
square wave response deteriorating after about 
25kc/s, after which considerable rounding off 
occurs. The waveform diagram shows a square 
wave with a frequency of 25kc/s as generated Yl 
trace and as reproduced at 1W output by a 10W 
amplifier on the Y2 trace. The rise time of the 
square wave was 2-0/*S (the oscilloscope shows this 
as absolutely square, no rounding off, overshoot 
or sag) and as the Yl trace is still reasonably 
square the performance of the gate as a whole can 
be considered to be eminently satisfactory — for all 
but the most exacting requirements anyway. 

The complete circuit of Fig. 3 will be seen to be 
quite simple when split into its individual stages, 
which will be considered in turn commencing with 
the gate generator VI. This is connected as a 
cross-coupled multivibrator, the traditional form 
of square wave generator. Although the cathode 
coupled multi is somewhat simpler and cheaper 
to build the necessity of providing two anti-phase 
outputs precluded its use in favour of the cross- 
coupled variety. The variation in the gating 
speeds is brought about by Sla and Sib, which 
selects two sets of five close-tolerance (2%) 
frequency determining capacitors, CI to C5 and 
C6 to CIO. Two methods of discriminating 
between the two Yl and Y2 traces have already 
been considered. It will be remembered that one 
method was offsetting the two traces so that they 
lay one above the other and the other method was 
making one trace brighter than the other by 
altering the mark space ratio. During initial 
development of the gating circuit it was decided 
that offsetting the two traces was undoubtedly the 
best method and it was thereby decided to make 
the mark space ratio as near to one to one as 
possible. Hence the close-tolerance capacitors 
which also confer another benefit upon the circuit. 
In conjunction with close tolerance (5%) grid leaks 
they ensure that no two positions of SI provide 
oscillations at or near identical frequency, which 
could possibly have occurred had wide-tolerance 
components been used. 



Time Constants 

The frequency of oscillation of a multi is 
approximately equal to 077 /CR where C is the 
value of one of the coupling capacitors and R the 
arid leak. Since large values of capacitors are 
correspondingly larger and more expensive than 
smaller ones" the two grid leaks Rl and R2 are 
made 1-5MCI, which means that the largest value 
of capacitor required is l.OOOpF. for fo=50c/s. 
For convenience in wiring the capacitors are wired 
in series so that the next capacitor value is 300pF 
(l.OOOpF and 470pF in series) and fo = l,700c/s. 
The frequency therefore changes in five steps of 
3-1 and makes it possible to select a gating speed 
most appropriate to the timebase speed within 
quite wide limit*. 



COMPONENTS LIST 
Resistors: 

All 20% £W except where stated. 

Rl I5MQ5% R9 \kQS% 

R2 l-5M0 5% RIO 22kQ 

R3 47ki"}5% RM 2-2Mii 

R4 47kQ5% RI2 2-7kii 

R5 4-7MQ RI3 55kQ 

R6 4-7MO RI4 lOMil 

R7 8-2kii I-5W RI5 220k£2 

R8 lkQ5% RI6 lkQ2W see text 

Potentiometers: 
VRI 500ft lin. VR2 IMQIin. 

VR3 IMftlin. 

Capacitors: 

2% silver mica except where stated. 

CI I5 P F2% C6 I5 P F2% 

C2 47pF2% C7 47pF 2% 

C3 I50 P F2% C8 I50 P F2% 

C4 470pF2% C9 470pF 2% 

C5 I OOOpF ceramic CIO I OOOpF ceramic 

CI I 0-ljtF 200V paper. See text. 

CI 2 0-l/xF 200v paper. See text 

CI 3 0-0 I^F 350V paper 

CI4 0- 1 ^F 350V paper 

CI5 lOOpF ceramic 

CI6 lOOpF ceramic 

CI7 0-l/xF 350V paper 

CI 8 32/zF 350V electrolytic 

CI9 0-25*tF 350V paper 

Valves: 
VI.V2, V3 I2AU7 V4 I2AX7 

Valveholders: 

4 B9A 
Switches: 

51 2 pole, 6 way, rotary 

52 I pole, 2 way, miniature slide 
Sockets: 

4 co-ax. 



Although the outputs from VI could have been 
applied directly to the Yl and Y2 amplifiers' V3, 
it was considered desirable to incorporate a 
cathode follower buffer stage V2 between VI and 
V3. The eating waveforms are therefore 
developed across R7, VRI, R8, the cathode loads, 
which are also common to V3, and V3 is therefore 
allowed to conduct and driven into cut-off, the two 
halves working in anti-phase. VRI varies the bias 
voltages, increasing one as the other is decreased, 
so bringing about trace separation in the manner 
already described. The outputs from the two 
halves of V3 are developed across the common 
load resistor R9 and are fed via CI 3 to the cathode 
follower output stage V4a. Tt had originally been 
intended to use direct coupling until the voltage on 
the anodes of V3 was measured and found to be 
165V. This would have necessitated a cathode 
voltage on V4a of about 170V, which it was felt 
was liable to put somewhat of a strain on the 
heater-to-cathode insulation of V4a. The output 
from the cathode of V4a was connected directly to 
the output socket without the customary coupling 
capacitor simply because the oscilloscope contains 
its own z.f. isolating capacitor and it was felt that 
two such capacitors in series were quite 
unnecessary. 



April, 1966 



PRACTICAL WIRELESS 



1079 



EXPRESS ELECTRONICS 

32 SOUTH END, CROYDON, SURREY 
Telephone: Croydon 9186 

FOR THE FOLLOWING BRAND NEW UNITS 

AMPLIFIERS AND TUNERS 



TRIPLETONE HI-FI MAJOR 


12 


watt 


£15.18.6 


TRIPLETONE CONVERTIBLE ... 


S 


watt 


£6.19.6 


TRIPLETONE GEMINI STEREO... 


s 


watt 


£15.15.0 


TRIPLETONE FM TUNER 






£15.14.6 


LINEAR 


3 


watt 


£6. 6.0 


LINEAR DIATONIC 


13 


watt 


£12.12.0 


LINEAR CONCHORD 


30 


watt 


£16.16.0 


LEAK TLI2 


M 


watt 


£18.18.0 


LEAK VARISLOPE PRE-AMP ... 






£15.15.0 


LEAK TL50 


Si 


watt 


£33.12.0 


LEAK TROUGH LINE 3 FM TUNER 




... ■• 


£31.14.6 


QUAD 


IS 


watt 


£22. 1.0 


QUAD STEREO/MONO PRE-AMP 







£25. 0.C 


LOUDSPEAKERS 






GOODMANS AXIETTE 8in. 


6 


watt 


£5. 5.0 


GOODMANS AXIOM lOin. 


10 


watt 


£6. 6.0 


GOODMANS AXIOM 201 


lb 


watt 


£10.15.0 


BAKERS 'SELHURST 


3 or 15 ohm 




STALWART I2in 


IS 


watt 


£5. 5.0 


BASS GUITAR I2in. 'Group 25" 


25 


watt 


£5. 5.0 


BASS GUITAR 'Group 35' 


)5 


watt 


£8.18.6 


BASS GUITAR "Group SO- 


so 


watt 


£18.18.0 


STANDARD Heavy Duty I2in. ... 


X 


watt 


£7. 7.0 


BASS Heavy Duty I2in 

AUDITORIUM 15 


is 


watt 


£12.12.0 


ib 


watt 


£18.18.0 


RECORD PLAYERS 






GARRARD MODEL 1000 4-speed MONO 


£6.19.6 


GARRARD MODEL 2000 MONO 




... #•• 


£7.15.0 


GARRARD MODEL 3000 STEREO 




• •• ■■ 


£10.10.0 


GARRARD MODEL 401 




... 


£29.10.0 


GARRARD MODEL LAB80 




... .. 


£24.10.0 


GARRARD AT6 TRANSCRIPTION MONO 


£9.17.6 


GARRARD MODEL AT60 






£11.15.0 


GARRARD MODEL A70 






£19.10.0 


GARRARD SRP 10 






£4.19.6 


Delivered free U.K. S.A.E. enquiries. 







NEW FROM PITMAN 

Telecommunication 
PrincipSes 

R. N. Renton 



One might have thought that a book on principles could 
have remained unchanged and valid indefinitely, but such 
has been the pace of developments in telecommunication 
during the last decade or two that a revised edition of 
this standard work was thought necessary. The biggest 
single change is a new chapter dealing with semi-conductor 
devices (Theory and Application). In addition the book 
deals with properties of new magnetic and dielectric 
materials (including square-loop materials and ferrites). 
The revised City and Guilds Syllabuses are fully covered 
and recent questions have been added to ensure that this 
textbook retains its high reputation for easy comprehen- 
sion and accuracy. 

New third edition 50s. net 

from all booksellers Pitman Parker St. London 



HIGH QUALITY 




LOWER COST 



Combine an Armstrong Tuner and Amplifier and you 
have all the advantages of separate units, plus com- 
pactness, easier installation, and equivalent perform- 
ance at a lower price. 

Stereo model 127, above, derived from the more 
expensive 227, has an identical AM-FM tuner section, 
with an amplifier section designed for those whose 
power requirements are more modest, 
it has a more modest price too, as does the mono 
version model I27M. 

Each Armstrong Tuner-Amplifier is Ideal as the basis 
of a high fidelity system for radio and record 
reproduction, tape recording, and playback, and each 
unit may be built into your own cabinet or used in 
our optional case, of teak and vinyl hide, as shown. 

For full details and technical specifications of all 
models plus list of over 300 stockists, post coupon or 
write mentioning 4PW66. 

model 127 STEREO TUNER AMPLIFIER £37.10.0 

model I27M MONO TUNER AMPLIFIER £26.10.0 

optional case £3.10.0 

AUDIO FAIR. ENQUIRY ROOM 539 

BOOTH 45 DEMONSTRATION ROOM 537 




Qwts&iottQ 



ARMSTRONG AUDIO LTD-WARLTERS ROAD-N.7 
Telephone: NORth 3213 



Address- 



4PW66 



1080 



PRACTICAL WIRELESS 



April, 1966 




TRANSISTOR POCKET RADIOS 

Ideal Gifts— all supplied complete with personal earpiece, 
battery and carrying: case. Fully guaranteed. Post Free. 

BOY'S 2TRANSISTOR MODEL (Illustrated) 

In attractive plastic case. Size only 4 x 21 r lin. 
2}in. speaker. Uses PP3 battery. Tunable over 
full medium waveband. 39'6 




BOY'S 4 TRANSISTOR MODEL 



45'- 



L 



t TRANSISTOR MODELS 

In plastic case. 4 x 21 x lin. with 2iin. speaker. 
Uses PP3 type battery. Tunable over full medium 
waveband. S9'6 

•i "waveband (Long and Medium) Model size 5 x 3, x llin.. 

crea m/black plast ic case. __^_ 89 '6 

FAMOUS MAKE TRANSISTOR RADIO 
THE "8TELLA" tfJHaMJaM 

:V ■ :'.■•':■.-■■' . ' ;,: 
7 transistor portable radio. Long, g 
Med. and Short wavebands. Fitted :; 
tone switch and sockets :or per- 
sonal earphone and external 
aerial: chrome telescopic aerial 
Uses four 1.5 v. torch batteries, §&&.- : 
Plastic cablnot in beige and rod. """raassssaiiSiafcBjjgs&f 
size 4 x 7 x liln. Excellent tone. 
3in. p.m. speaker. Comp. with shoulder strap and external aerial. 
Full guarantee. List price 17 tins. «q iqc .»«■»« 

WIRECOMP'S PRICE fcO.lS.D P. & P. 5'- 



««*.* 



WONDERFUL BARGAIN FROM RUSSIA 
THE "SOKOL" 

7 transistor radio covering full Medium and Long wavebands 
with exclusive rechargeable battery which can be recharged 
from any 110/250 v. A.C. mains supply. Can also operate on PP3 
tyoe dry battery. High quality P.M. speaker. Ivory and black 
Maatto esse with metal trim— size 6 x 3i x Win. Sockets for 
external aerial and oamlece. Complete with real leatner case, 
dry battery, rechargeable battery and charger, personal ear- 

£6.9.6 



WIRECOMP'S PRICE 



P. & P. 2'6 



WIR ECOMP'S SALE! 



WIRECOMP'S SALE! 

WIRECOMP'S SALE! 

THIS MONTH ONLY AT ALL 
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323 Edgware Road, W.2 
378 Harrow Road, W.9 

Fantastic Reductions on Thousands of lines — 
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Radiograms — Amplifiers — Tuners — Components 
Chassis — Speakers — Microphones etc. etc 

DON'T MISS IT 



INTERNATIONAL BRAND 

MYLAR BASE 

3{in Triple play. 600ft. 15/- 

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5?in, Double play. 1.800ft. 22/6 

5lin. Triple play. 2.400ft. 45/- 

7in. Stand, play. 1,200ft. 12/6 

7in. Long play. 1.800ft. 19/6 

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7in. Triple play. 3.600ft. 58/6 
P. & P. 1/- extra per reel. 4 



TAPE — Fully Guaranteed 

ACETATE BASE 

3in.— 150ft. 3/6 

3in— 225ft 4/11 

3in.— 300ft. 7/6 

Sin. Long play, 900ft. 107- 

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7in. Stand, play. 1.200ft. 10/- 

71n. Long play. 1.800ft. 15/- 
P.V.C. BASE 

Sin. Stand, play. 600ft. 8/6 

5Jin. Stand, play. 840ft. 11/6 
reels and over Post Free. 



323 EDGWARE RD., LONDON, WJL »M«»*»r 

AM Breaches opes, sii day Saturday. Early closing Thursday 



378 HARROW RD., LONDON, W.9. cuM-ingtam 

Mail Orders to the above address for prompt service 



TTfFfMM 



- THE LATEST EDITION OF ENGINEERING OPPORTUNITIES 



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April, 1966 

TRACE DOUBLER 

—continued from page 1078 
V4b is arranged as the sync amplifying and 
limiting stage, more as a matter of wiring 
convenience than electrical necessity. The pro- 
vision of a suitable sync signal is rather more 
involved than would be apparent at first. During 
the gate's early stages trouble was experienced 
with synchronising the trace using the internal sync 
position of the oscilloscope. A certain amount of 
jitter plus a reluctance of the trace to stay 
synchronised was finally put down to the gating 
waveform, the frequency stability of which is not 



PRACTICAL WIRELESS 



1081 



particularly good. The sharp leading edge of its 
square wave, however, synchronised the oscillo- 
scope's timebase much better than a sinewave input 
having a much higher frequency stability, with the 
result that the sync tended to " wander " with the 
gating waveform. Once this was realised the sync 
signal was extracted before being gated and was 
fed into the oscilloscope, switched for external 
sync, with the result that jitter was absent and the 
timebase stayed synchronised to the input signal. 
S2 allows either the Yl or the Y2 signal to syn- 
chronise the timebase. 

CONTINUED NEXT MONTH 







Fig. 4: Chassis wiring. The centre spigot of V2 is used as an h.t.+ point. 



Reflex 2 

—continued from page I0S9 

twists on this coupling were sufficient to put the 
r.f. amplifier in oscillation over the entire band. It 
was found that just a single twist is sufficient for 
most purposes, depending upon the nature of Trl. 

Capacitor CI in the tuned circuit of LI consti- 
tutes a form of padding capacitor, as well as serving 
as an r.f. bypass. Thus, the tracking can be 
influenced by varying the value of this component. 
Unfortunately, there is not available a miniature 
preset capacitor of sufficiently high value to permit 
easy adjustment here. The author found that an 
0-005/'.F fixed capacitor satisfied the tracking for his 
reception area, but values above or below this could 
be tried since CI is not difficult to change. 

It is as well to remember that a simple set of 
this kind employing a sub-miniature ferrite rod 
aerial and only two transistors cannot be claimed 
to have super-sensitivity! Nevertheless, the proto- 
type gave good volume on local stations, while after 
dark the more powerful European stations were 
received. 

Housing the Receiver 

The complete receiver is fitted in a small ready 
drilled plastic case as shown in the photograph 
which comes with back, tuning knob and paper 



dial. The gang retaining nut being used to lock the 
assembly to the front panel and a hole in the side of 
the box to cater for the jack socket which, again, is 
held secure by its locking nut. The long 6BA bolt 
on the rear of the tuning gang is used to hold the 
back of the case in position. 

The battery will have many months of useful life 
provided the earpiece jack plug is removed from 
the socket when the set is not in use 



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hold normally 12 issues. Please state volume number 
required otherwise a blank cover will be sent. 

A new version of the Easi-binder with a special 
pocket for storing blueprints and data sheets is now 
available. The price is 1 1 '6d inclusive of postage. 

Order your binder from: Binding Department, 
George Newnes Ltd., Tower House, Southampton 
Street, London, W.C.2. 



A SHORT SERIES FOR THE EXPERIMENTER 



OSCILLATOR 
CIRCUITRY 



*%>%%** 



R. Leyland 



2— DESIGN OF TRANSISTOR OSCILLATORS 



WHEN average transistors are used at low 
voltages two transistors will probably be 
necessary as a minimum in a resistance- 
capacitance oscillator. An advantage of the two 
amplifying stages as compared with a single 
transistor is that positive feedback can be obtained 
directly without resorting to the 180" phase shift 
of a ladder network. Simpler forms of network 
can therefore be used which have zero phase shift 
at the frequency of oscillation. 

Wien Network 

The most widely used of these is the Wien 
network (Fig. 3a), which has several less familiar 
variations, including current duals. The output 
from these networks reaches a peak equal to one- 
third of the input at the frequency where the phase 
shift becomes zero. With the surplus of amplifica- 
tion usually available the oscillator can be 
stabilised by an appreciable amount of negative 
feedback applied to reduce the loop gain to unity. 

On subtracting the output of a Wien or similar 
network from its input to give the inverse response, 
i.e. by taking the new output from the other part 
of the network, a valley type response is obtained 
with a minimum equal to two-thirds of the input 
at the frequency of zero phase shift. In a true null 
network the minimum output would, of course, 
fall to zero. 



Very low P^^ R 
impedance I 
source JL 

Vin© 



>—o 




(a) Input conversion 



Very low 

impedance 

load 



Very high 
Impedance 

load 



=— — vVVW- 



lom-voyt 



Vout 



(b) Output conversion 

Fig. I : Alternative arrangements at end of network where 
there is a resistance. 



This form of network, e.g. a bridged-T (Fig. 4a), 
can be utilised in a negative feedback path, but a 
large amount of positive feedback is required in 
an auxiliary positive feedback loop to bring about 
oscillation, so it is quite a difficult type of network 
to use successfully in the simpler types of 
oscillator. Since the net feedback will be positive, 
conditions approximate to those in a Wien bridge 
oscillator because when the input is a blend of 
positive and negative feedback it can be influenced 
by a phase shift in either. 

Parallel-T 

The true null network is a parallel-T. Although 
it has a rather different form of phase-shifting 
characteristic it can be substituted for the 
bridged-T network and, since the negative feed- 
back now disappears altogether at the frequency of 
oscillation, considerably less positive feedback is 
required in the auxiliary loop. 





Very high 
Impedance load 












Very low |~^ 

imparlance 
source 1 


"J' 






"1 


T 















Very low 
Impedance load 




Very high ["" ° 
impedance 1 

imp 


Tzi 

[p lout 



















(a) Potential divtter (b) Current divider 

Fig. 2: Single stage networks. 

The Parallel-T can likewise be rearranged to give 
an inverse response, which is a peak at zero phase 
shift, equal to the input and therefore three times 
that of the Wien network. Decreasing the 
impedance of the low-impedance branches will 
increase the output slightly above the input and 
it can then be used in an emitter follower type of 
oscillator where the actual voltage gain of the 
amplifier is less than unity (Fig. 7). 

The disadvantage of the Parallel-T network is 
that it requires three capacitors and three resistors. 
The values of these are not all alike and require, 
for the null circuit, to be in a certain ratio, usually 
2:1:1 as in Fig. 4b. 

Tuning 

In variable frequency oscillators tuning is easily 
accomplished by means of resistance capacitance 
networks. With their wide tuning range it is 
possible to cover from a few cycles per second to 



April, 1966 



PRACTICAL WIRELESS 



1083 



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April, 1966 



MINIATURE 
METALLIZED 



POLTESTER 



CAPACITORS 



Ideally suitable for printed wiring panels and 
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April, 1966 



PRACTICAL WIRELESS 



1085 




(c) Output conversion 



(a) Capacitances transposed 1 - 



Fig. 3: Variations on the Wien network. 

the lower radio frequencies in four ranges of 
switched capacitances, usually with a 10:1 ratio 
between adjacent ranges, and ganged potentio- 
meters employed for fine tuning provide scales of 
about 300°. The potentiometers are normally 
wire wound to an inverse semi-log characteristic 
and of adequate resolution to enable a large-scale 
and sufficient accuracy of setting to be obtained. 

Networks of the Wien type require only two 
capacitors to be switched per range and a dual- 
ganged potentiometer, by varying both of the net- 
work resistances simultaneously, avoids changes in 
the attenuation of the network, although altering 
the impedance it presents to the amplifying section. 
The amplifier normally requires to have a very low 
output impedance (and high input impedance), 
assuming a voltage transfer network, to avoid 
variation of the amplitude with tuning. A 
thermistor will probably be included to compensate 
for amplitude variations but it is advisable not to 
delegate too much of the task to the thermistor. 

Amplifier Phase Shift 

As far as possible all the frequency dependent 
phase shift should be concentrated in the R-C net- 
work, where it is determined entirely by passive 
components. The amplifier should be constant in 
performance and independent of frequency. 

At high frequencies internal phase shift in the 
transistors can be minimised by employing r.f. 
transistors. At low frequencies amplifier phase 
shift can be overcome by means of direct coupling. 
A positive feedback loop nevertheless must 
normally contain a blocking capacitor to prevent 
it from exerting an unstabilising effect on the 
quiescent points of the transistors, but this may be 
one of the capacitors of the phase-shifting net- 
work. A negative feedback loop, on the other 
hand, has a stabilising effect on the d.c. levels and 
so may with advantage be direct coupled through- 
out. 




Impedance Levels 

Considering the frequency response as concen- 
trated in the network assumes that the amplifier 
and network act independently. At both ends of 
the network, however, variable loading effects, if 
present, can interfere with the frequency response, 
making it less predictable and constant. Ideally 
the neFwork must neither load or be loaded by the 
amplifier and instead of an impedance match for 
maximum power transfer the impedance levels of 
the amplifier and network should be widely 
different. This is necessary also to avoid distortion 
due to the non-linear input impedance of a 
transistor. 

There are two ways of minimising the effect or 
a load variation. One is to make the source 
impedance much lower than that of the load, in 
which case the voltage remains nearly constant. 
The other method is to make the source impedance 
much higher than the load, in which case the 
current is nearly constant. When the source 
impedance is zero it is called a voltage generator 
and when the source impedance is infinite it is 
called a current generator. Each is represented by 
a special symbol in diagrams as in Fig. 1. In 
practice it is a question of the ratio between source 
and load impedances and we can speak of a 
'" voltage input " when negligible voltage is 
developed across the load. 




(a) Bridged— T 



(b) Parallel-T null network 



Fig. 4 : Networks with valley-type responses. 



Fig. 5: Oscillator with modified Wien network. 

A voltage transfer network, which subjects a 
voltage to Its frequency response, can only be used 
when^an amplifier has a low output impedance and 
a high input impedance relative to the impedance 
level of the network. For a current transfer net- 
work the reverse conditions apply. 
High input impedances and low output impedances 
in the amplifier can be secured by the use of 
emitter-follower stages. A special arrangement 
may be necessary for the bias supply to the base 
of the input emitter-follower, since a d.c. path 
must be maintained via a resistance to every 
electrode of a transistor. The high amplifier 
output impedance that is required for a current 
transfer network can only be provided easily when 
one of the resistors of the phase-shifting network 
serves also as a collector load resistor. 



1086 



PRACTICAL WIRELESS 



April, 1966 



Network Duals 

Voltage transfer networks can be regarded as 
composed of various potential dividers containing 
resistances and capacitances. Since two impedances 
in parallel constitute a current divider (Fig. 2b) it 
is possible to build current transfer networks on 
close analogy with the voltage transfer networks. 
To every voltage transfer network there corre- 
sponds a current transfer network called its current 
dual and it can be derived, for all the three- 
terminal networks we are considering, simply by 
turning the network round so that the input and 
output change places. The amplifier impedance 
levels must also be interchanged. 

It is shown in Fig. 1 that a voltage generator in 
parallel with the resistance is equivalent to a 
current generator in parallel with the resistance. 
This is less obvious than the corresponding output 
conversion based on the current through a 
resistance being proportional to and in phase with 
the voltage across it. 

It is convenient to be able to alter the feed 
arrangements of a network in this way but if the 
change is made only at one end the network main- 
tains its frequency response but now derives an 
output voltage from an input current, or vice versa, 
so that the amplifier impedances can be both 
higher or both lower, as the case may be, than the 
network impedance. 

A similar conversion can be made with capaci- 
tances at the ends of the Wien network if the 
change is made at each end so that the phase shifts 
cancel. By applying all of the preceding transfor- 
mations to the Wien network quite a number of 
other networks with a similar frequency response 
can be derived. Some of these are shown in 
Fig. 3. 

Networks appear to consist of simple sections 
but the loading of later sections upon earlier ones 
makes analysis more complicated. Separation of 
the sections of some networks is possible by 
inserting isolating stages between them, but this 
would be unusual in a transistor oscillator since it 
would increase the number of transistors. 

Oscillator Circuits 

It is possible to overrate current duals as 
oscillator networks and the typical a.f. oscillator 
uses a Wien network, which is of the voltage 



3-9kn 





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3mA 



Heft 



Amplitude 

135? 100pF 



— — vVvW-— ; vV*AA£; — J|— 



r \Aj 



Output 



10W1 



2'2kn 





Fig. 6: Parallel-T — ve feedback oscillator. 



Fig. 7: Parallel-T -{-ve feedback oscillator. 

transfer type. This requires a high input 
impedance in the amplifying section and with 
transistors this can be obtained from a compound 
emitter-follower arrangement involving two tran- 
sistors. A third transistor will be necessary to 
secure a low output impedance and the amplifier 
must provide voltage amplification without phase 
reversal. The best direct-coupled arrangement 
combines p-n-p transistors with n-p-n. Increasing 
the number of transistors in an oscillator allows 
greater scope in design, enables the performance 
to be improved and permits variable tuning. 

In a two transistor oscillator the possibilities are 
more limited, especially with direct coupling, and 
with less orthodox circuits snags are encountered 
such as the provision of satisfactory forms of 
amplitude control to prevent limiting. 

The oscillator shown in Fig. 5, however, has a 
good performance and only consumes 05mA of 
current. It contains a Wien network supplied 
from the low-output impedance of the upper 
transistor, an emitter- follower, and from the Wien 
network an output current enters the emitter of the 
lower transistor, a ground-base stage, whose 
collector load resistance is increased in value 
artificially by the bootstrap action of the upper 
transistor. The current gain of the emitter- 
follower depends upon a sufficiently low 
impedance in its output circuit, hence the low 
resistance values in the network, but the equal 
capacitors C can be given a range of values to 
yield various spot frequencies. Amplitude control, 
gradual in action, is by varying the impedance in 
the base circuit 

The oscillator of Fig. 6 employs a Parallel-T 
null network in a negative feedback path. A 
Bridged-T would not give such a large undistorted 
output. Positive feedback between the emitters is 
varied for amplitude control. 

An even better oscillator using a Parallel-T is 
shown in Fig. 7. In this optimum amplifier 
conditions can be secured with very high input 
impedance and a low output impedance. The low- 
impedance arms of the network are made lower in 
impedance than for a null network in order to 
step up the output voltage to the base of the first 
transistor. Amplitude control is by a resistance 
between the transistors but the low-resistance 
branch of the network could be varied instead. | 



April, 1966 



PRACTICAL WIRELESS 



1087 



BROADWAY ELECTRONICS 

92 MITCHAM ROAD, TOOTING, S.W.17 

Phone : BALham 3984 

(four minutes from Tooting Broadway Underground Station) 



GARRARD 4 SPEED DECKS WITH CARTRIDGE: Auto- 
changers: AT60. £10.0.0: 3000, £8.8-0; 2000. £7.7.0; 1000 £6.8.0: 
Autosllm £5.5.0; De Luxe Autoslim with plug-in head. £5.15.0. 
P. & P. 6/-. Single Players: SP25. £10.10.0: SHP12. £5.0-0; Garrard 
Plinth. W.B.I. £3.12.6. P. & P. 4/6 for plinth. Motor boards 
6/6 each. 

CARTRIDGES: Ronette Stereo 25/-: Acos GP67. 157-; G.C.2 
Garrard 15/-; AT6 shells 5/-. P. & P. 6d. HGP83/2 Stereo 20/-. 
SPEAKER ENCLOSURES: "TONY" Corner Cabinet 20 x 10 x 
Tin., takes 10 x 6in. speaker, covered In grey Rexine and vynair. 
45/-, P. & P. 5/-. "BLAKE" Heavy Duty Cabinet with port. 
241 x 18 x 9in. Baffle jin. thick. Covered Rexine and Vynair. £5. 
P. & P. 10/-. Extra baffle for 8 or 10in.. 3/6. "BLAKE DE LUXE" 
veneered with wood-grain Formica and standing on smart 6in. 
legs. £6.5.0. P. & P- 10/-. ••HAYDON" 16$ x 15 x 7|in.. fabric 
covered, suitable 12in. speaker, 45/-. P. & P- 7/6. Crystal Mike 
200C replaces BM3, 30/-. P. & P. 2/-. Stand for same. 9/6. P. & P. 
J/9. Guitar Pick-up with Screened Lead. 12/6- P.&P. 6d. Crystal 
Lapel Mike, 7/6. Neon Panel Light Arcolectric 240v. A.C., 2/6. 
P. & P. 6d. Tape Spools: 3ln.. 9U.; 41n.. 1/-; 5in., 1/3; ojm.. 1/9; 
7in.. 21- each. 

BARGAINS IN TRANSISTORS. AC127. AF 114. 115. 116 117. 
118, 119. OC169, 170. 171, 172, 5/6 each. OC72. 75. 82, 3/6. OC71. 
81M, 3/-. RF Packs— 1 OC44. 2 OC45. 8/6. AF Packs— 1 OC81D, 

2 OC81, 6/-. AF Pack— 1 GET118, 2 GET119. 5/6. OC26. 28. 29. 7/6. 
ORP12 Light Cell. 7/6. Diodes OA81. 2/3, OA91. 1/9. P- & P. on all 
these 6d. 

EARPD2CES with cord and 3.5 mm plug, 8 ohm magnetic 3/-; 
250 ohm, 4/-: 180 ohm Magnetic with clip. 6/6; Crystal. 4/-. P. & 
P. 6d. 

SPEAKERS: ELAC Heavy duty Ceramic Magnet, 11.000 lines. 
lOin. round, 10 x 6, 15 or 3 ohm. 42/6- P. & P- 3/6. 8in. round Id or 

3 ohm. 38/6. P. & P. 3/6. EMI 131 x 8in. 15 or 3 ohm. 42/6. P. & 
P. 3/6. 

Stockists for Eagle Products. Goodmans. W.B., Wharfedale, 
Bakers. TriDletone. Linear, all makes of amplifiers and speakers 
supplied. Let us quote for your requirements. S.A.E. please. 
NO C.O.D. Trade terms to bona fide dealers. 



YOUR CAREER in 



ELECTRONICS? 

Big opportunities and big money await the qualified 
man in every field of Electronics today — both in the 
U.K. and throughout the world. We offer the finest 
home study training for all subjects in radio, television, 
etc., especially for the CITY & GUILDS EXAMS, 
(Technicians' Certificates); the Grad. Brit. I.R.E. Exam.; 
the RADIO AMATEUR'S LICENCE; P.M.G. Certificates; 
the R.T.E.B. Servicing Certificates; etc. Also courses in 
Television; Transistors; Radar; Computers; Servo- 
mechanisms; Mathematics and Practical Transistor Radio 
course, with equipment. We have OVER 20 YEARS' 
experience in teaching radio subjects and an unbroken 
record of exam, successes. We are the only privately 
run British home study College specialising in electronic 
subjects only. Fullest details will be gladly sent without 
any obligation. 

To: British National Radio School, Reading, Berks. 

Please send FREE BROCHURE to: 

___Block 

f*jpt. 



NAME- 



ADDRESS 



..Please 
4.66 



BRITISH NATIONAL RADIO SCHOOL 





Extend the range of your present test instrumentation with 
this versatile Telequipment oscilloscope. Simplified operation — 
minimum controls, automatic time base synchronisation — but 
top quality construction. 

2.75in. tube with graticule, contrast filter and rubber light 
hood. Bandwidth DC-30Kc/s (-3dB); maximum sensitivity 
lOOmV/O.ocm division. Time base continuously variable from 
lOOusccs to lOOmsecs per 0.5cm division. Mains operated, 
fully portable. Instruction manual supplied. 
Descriptive leaflet on request. 

Obtainable only direct from the country's largest specialist 
manufacturer of portable oscilloscopes for science and industry. 
Serviscope is a registered trademark 

TELEQUIPMENT 



Telequipment Ltd., 313 Chase Rd., Southgate. London N.14 
Tel: Fox Lane 1166 

Please send me, without obligation, tha 
descriptive leaflet on the Serviscope Minor. 



NAME.. 



ADDRESS. 









1088 



PRACTICAL WIRELESS 



April, 1966 



HOME RADIO LTD. 187 LONDON RD., MITCHAM, SURREY 'Phone MIT 3282 

ARE YOU LOOKING for the UNUSUAL! 

Because it may be standard catalogue 
stock to us. Here are a few examples 

THERMISTORS 




Type R.53 .., 
Also stocked: 
A.I5... I2'6 . 
A.26 ... I2'6 . 
A.54 ... I2'6 . 



... £1.1.0 

A.55 ... I2'6 

R.24... £.1.1.0 



HIGH VOLTAGE RECTIFIERS 

K3/40 9'- 

Also stocked: 

K.3/15 6'- 

K.3/50 I2'4 

K.3/100 ... £1.0.3 
S.T.C. FM CRYSTALS £3.15.0 K.3/160 ... £1.5.6 



GANGED STEREO 



POTS 

I OK Log |- lOKA'Log 10'- 
I0K Log -; I OK Log D.P. 

switch I2'3 

Also stocked: 

(Log or Linear) I0K, 50K, 

I00K, 250K, IM, 2M 10'- 

All the above and many thousands of other electronic 
items, both usual and unusual, may be found in our 
catalogue, price 7'6, plus I '6 postage and packing. 
Each catalogue contains 5 coupons each worth I'- 
ll used as directed. Post the Coupon on the right with 
your cheque or P.O. for 9'-. 




RESISTORS 




i — I, nri »°/- a wa« 


■jg— a'rrfrire»|» Most values between ll 


—J 1 Ohms and 10 Meg. 2'- 


VALVES 


85AI... £2.11.6 


TT2I ... £2.8.6 


VRI05/30 18/6 


85A2 ... I5'6 


EN9I ... £1.6.0 


VRI50/30 I8'6 


Z803U ... I8'6 


I50B2... I5'4 


6141 ... £2.0.0 


I50C4 ... 15*9 


QVO6/20 


5763 ... £1.0.0 


OA2 ... 15'- 


£2.8.0 


OB2 ... 16'- 


ALSO MATCHED PAIRS 


OAZ222 . 


.. £1.6.0 
I7'6 
14'- 


OAZ224 . 


TRANSISTORS & DIODES 


AFI86 £1.7.6 GETI03 ... 7'- OC76 ... 7'- 


ACI07 ... I4'6 


GETI06 ... 17'- 


OC77 ... 12'- 


BYZI3 ... Il'6 


GETII5 ... 9'6 


OC83 ... 6'- 


ASY28 ... 8'6 


GETII6 ... 17'- 


OC84 ... 8'- 


GEX66... 15'- 




SVCI ... 28'- 



Please write your name and address in block capitals | 

I 



NAME ... 
ADDRESS 



I 



HOME RADIO LTD.. DEPT. P W., 187 LONDON ROAD, MITCHAM I 



RADIO CLEARANCE LTD. 

[27 TOTTENHAM COURT ROAD, LONDON W.I. Telephone: MUSeum 9188] 
t Bulk enquiries invited. The oldest components specialists in the trade. Est. 35 yrs. 1 

LOUDSPEAKER BARGAINS STILL AVAILABLE 

1 Enormous purchases of Brand New and Guaranteed Pli-s>ey loudspeaker* 
I enable us to offer these units at TIIK LOWEST PRICES EVER] Don't miss this 
I Kolden oppornmltj to obtain a first-trade permaneiit-niag-nei LOl nsi'KAKKK 
1 off the production line at I.KSS THAN THE M AM I'ACTCKKICS COST! Read I 
. earelull> the prepared list below and elioose lust the right speaker lor the lob— 1 
' CO MP \H I. Till-: PRICES ANYWHERE! SELLING FAST— STOCKS CHANGING ( 
1 RAPIDLY. 



Site Gauss 



•2\ 7000 
■-■;■ 7000 
•-•1 7000 

:t ssoo 

3 7000 

a 701x1 

.1 6500 

. • ..;■ ... 
3'. 7000 

5x3 

5 x X 

6 x :, 

5X3 
6X4 

8x4 

« s. .< 



Qauts Jmpeit. 



inc/ieA linr.t 

:ti 9500 

:;. not) 

::. M<M 

I MOO 

•I 7000 

J BOO 

t 0000 

i MOO 

1 KM 



Print 

10/6 
8/6 
10/8 
10/8 
11/- 
0/6 
11/6 
11/6 
12/- 



9000 


as 


12/- 




7000 


7000 




8/- 
8/6 




1I50U 


0000 


3 


7 y. 81 


050O 


0500 


s 




7x4 


0500 


8300 


3 


7x4 


0500 


0500 


3 


10/- 


7x4 


101 100 


9500 


33 


12/- 


7x4 


12000 



Prtcr) 
11/8 
8/6 I 
9/. I 
10/8 ( 
18/8, 
10/8 
11/- 



8/6 > 
9/-I 
10/- 1 
22/6| 
22/6) 
23/6 1 



ALLOW 2/6 eneh Speaker for postage and packing and handling charge and please | 
specify the exact requirements — the noarest available will he sent. 

SELECTED BARGAINS 

> Beautifully geared AM/FM 2-gang Condensers. 4/6: AMf FM IFT'S 465 kc/s and 10.7 Mc/s j 
I 4/6 pair: Magnavox Crystal Tape Recorder Mikes. 12/6: 3 watt Stereo Amplifiers. 
i complete, ready to switch on. 79/6: Sentercell rectifiers R3/2D-D3-2-1-Y, 2/6 each.' 
I DIODES— OA79. OA90, CO-16H, GD10. 2/- each. I 

TRANSISTORS: OC45 4/6. PXA101. 3/9. AMU, 4/6. Sub min. Germanium diode 1/3. 1 
Ml diode 6d. each. Silicon diodes. 400 p.i.v.. 330mA. 2/6 each, please send STAMPED ( 
'and ADDRESSED envelope with any enquiry. We regret no catalogue— our stocks ( 
• move too quickly! Kindly make provision for additional postage and package charge , 
I to avoid delay. Terms; Cash Willi Order or C.O.D. on Orders over 10/-. 



1966 EDITION 

RADIO AMATEUR 
HANDBOOK 



40'- 



Postage 2/6 



by ARRL 

TRANSISTOR POCKET BOOK by 

R. G. Hibberd. 25'-, Postage I'-. 

ELECTRONIC ORGAN HAND- 
BOOK by H. Emerson Anderson. 
35'-, Postage I'-. 

A LABORATORY MANUAL OF 
ELECTRONICS by K. J. Dean 20'-, 
Postage I'-. 

TRANSISTOR ELECTRONIC 

ORGANS FOR THE AMATEUR 
by A. Douglas & S. Astley. 18'-. 
Postage I/-. 

A BEGINNER'S GUIDE TO 
RADIO Pub. Ncwncs. 8'6, Postage 
9d. 

SERVICING AGC by H. E. Thomas 
28'-, Postage I-. 

A BEGINNER'S GUIDE TO TELE- 
VISION Pub. Newnes. 8'6, Postage 
9d. 

BASIC THEORY 8> APPLICATION 
OF TRANSISTORS by U.S. Dept. 
Army. 10'-, Postage I/-. 

COMPLETE CATALOGUE I'- 

THE MODERN BOOK CO. 

BRITAIN'S LARGEST STOCKISTS 
of British and American Technical Books 

19-21 PRAED STREET 
LONDON, W.2 

Phone: "Aldington 4ldS 
Open 6 doys 9-6 p.m. 




CITY OF BELFAST 
Y.M.C.A. RADIO CLUB 



ONE of the international Y.M.CA.'s most 
senior organisations. City of Belfast Y.M.C.A. 
Radio Club (GI6YM), is among the oldest 
radio clubs in the British Isles. The Club was 
founded in 1922 and received its transmitting 
licence and callsign in 1927. but there is some 
evidence of previous activity dating back to shortly 
after the close of World War I. It may be 
interesting to note that the Club licence holder, 
Mr. Robert Barr (GI5UR), a "call" well known 
to the world's c.w. DX fraternity, has been con- 
tinuously in membership since those early days 
and is still one of 6YM's most active members. 

The lifetime of GI6YM spans the history of 
radio experimentation in the north-east corner of 
Ireland and thus the City of Belfast Y.M.C.A. 
Radio Club can rightly be considered as the 
" cradle " of amateur radio in the most populous 
region of the six Irish counties comprising 
Northern Ireland. Certainly the majority of radio 
men and enthusiasts in the Belfast area, many of 
whom have made their mark on the " ham " hobby 
or in the wider radio world outside as Government 
scientific officers, Post Office, BBC and service 
technicians and operators, have all been connected 
with GI6YM at one time or another 

In the Y.M.C.A. tradition of "Service, Not 
Self" the Citv Club membership takes modest 



pride in its record during World War II days and 
was one of the few clubs which " carried on " 
in spite of cessation of transmitting activity and 
the loss of many of its most active members — of 
all ages — to the Royal and Merchant navies, Army 
and R.A.F. or engaged in security duties at home. 
Through its connection with the parent Y.M.C.A. 
— " Mecca " for thousands of Service men passing 
through Belfast — the City Club kept " open 
house" for Service "hams" from all over Ireland, 
Great Britain, the Commonwealth and the U.S.A. 
Many of these men held club office while stationed 
in Northern Ireland and needless to say, the war- 
time visitors' book is one of the most treasured 
items in the club archives. 

Club accommodation is second to none and 
comprises a general clubroom on the third floor of 
the main city Y.M.C.A. building with a trans- 
mitting room on the floor above. The clubroom, 
recently refurbished in contemporary "decor", 
contains comfortable seating (including settee and 
easy chairs!) library with technical and current 
British and U.S. radio publications, listeners' 
corner complete with junior HRO, Morse practice 
equipment transcription record player and hi-fi 
amplifier for the club's audio section. 

The well-appointed transmitting room on the 
floor above contains most of the equipment 

II 




As a YMCA organisation GI6YM's emphasis has always been on youth. Pictured are some of the Club's SWL members 
and "junior ops." On the extreme left is GI3UKS, Dave Vizard, the area's youngest licensee. 



1090 



Jit ffiM-t:;: 



PRACTICAL WIRELESS 




April, 1966 



Left: Making checks on the Club's 
new S.S.B. transmitter are (from left) 
R. Barr (GISUR), SWL Evans, F. Robb 
(GI6TK) and Major Ian Kyle % club 
member and local T.A. "boffin". 



Below: Tuning-up the standby TIIS4 
transmitter are (from left) T. J. Moss 
(GI3UFH) Club treasurer, J. Beattie 
(GI3NQH) Club chairman, C. Rourke 
(GI3IVJ) Club secretary, licence-holder 
R. Barr (GI5UR) and SWL member. 



necessary for efficient operation 
under present-day conditions (the 
club recently made DXCC in 
spite of restricted hours of opera- 
tion), the gear comprising a 
KW77 receiver, medium-power 
c.w. transmitter for 80 40 and 
20m, 4m transmitter/receiver and 
all ancillary equipment. S.S.B. 
operation is also engaged in 
using a Sphinx transmitter, until 
the construction of the Club's 
own all-band S.S.B. rig is com- 
pleted. 

Main aerial requirements are 
taken care of by the recent con- 
struction and erection of a line 
tri-band quad and supporting 
tower which has been mounted 
on one of the Y.M.C.A. build- 
ing's highest points overlooking 
busy Wellington Place and 
already a city landmark. This 
erection also carries the v.h.f. 
aerial and will eventually be 
remotely controlled from the transmitting position. 
The emergency aerial is an all-band trap dipole. 

The City of Belfast Club takes a full part in all 
local, national and international "ham" radio 
activity, chief among these being National Field 
Day and the popular Jamboree-on-the-Air, both 
events being held in conjunction with City 
Y.M.C.A.'s own Scout troop, which has a splendid 
QTH on the south side of the city. 

Regular meeting nights are held each Wednesday 
and Saturday evenings from 8 o'clock but activities 
such as Morse practise and construction take place 
on other evenings as required and access to the 
club is available at all times. Any enthusiast — 
transmitting or SWL — whether " local " or just 
passing through can be assured of a real Irish Cead 
Mile Failte in the best " YM " tradition. Club 
secretary is Mr. Cedric Rourke, GI3IVJ, 32 Kirk- 
liston Park, North Road, Belfast 5. 




TECHNICAL BOOKS IN NATIONAL LIBRARY WEEK 
121h— 19th MARCH 1966 

The first British Xatiunal Library Week will take place 
trum 12th lo 19th March 1000. The purpose is to interest 
everyone in making more use of libraries and in building 
up their own personal libraries. Local committees through- 
out Great Britain will be organizing book exhibiUons, 
talks, competitions, and other features. 
Scientific and technical books will be specially featured by 
many centres, with displays of students' textbooks, 
industrial books and 'do-it-yourself books. Talks by 
authors of scientific and technical books have been 
arranged, und some centres are staging exhibitions and 
discussions. 

Further information about National Library Week can be 
obtained from F. N. Radford Limited, 280-293 High 
Holborn, London, W.C.l. 



April, 1966 



PRACTICAL WIRELESS 



1091 



TAKE IT WITH YOU EVERYWHERE 

SI 




Not only is the SINCLAIR MICRO-6 
the smallest set in the world — it is the 
most efficient of its kind. This set has 
already been built by more constructors 
than any other kit in the history of tran- 
sistor sets and thousands more are being 
built each month. It is easy to see why. 
The power and selectivity of the MICRO- 
6 are remarkable by any standards. Its 
minute size and design are irresistibly 
attractive and it even has vernier-type 
tuning for easy station separation. 
Building is simplicity itself — the instruc- 
tions make success assured from the 
moment you unpack the parts for your 
MICRO-6. Everything is guaranteed, 
and a full time service department is 
available should you want it so that you 
cannot possibly go wrong. The MICRO- 
6 tunes over the medium waveband with 
bandspread to bring in Luxembourg like 
a local station. In fact, this little giant of a 
set will bring in programmes where 
larger sets sometimes cannot be heard at 
all, for it plays virtually everywhere. 

Until you have experienced the thrill of 
owning your own MICRO-6, you will 
never know just how exciting radio 
can be. 

m size i«// x i 3 / 10 * x v 

■ WEIGHT GBS.) I oz. 

■ PLAYS ANYWHERE — IN 
BUS, CAR, TRAIN, Etc. 

■ BANDSPREAD FOR EASY 
LUXEMBOURG RECEPTION 

■ A SINCLAIR GUARANTEED 
DESIGN 



The Worlds smallest radio 



6 STAGE POWER 
AND SELECTIVITY 

In the Sinclair Micro-6 three 
special Sinclair Micro Alloy 
Transistors (M.A.T.s) are 
used in a six stage circuit to 
provide two stages of R.F. amplification 
followed by double diode detection 
and a high gain three stage audio fre- 
quency amplifier. Signals are received on 
the special self-contained ferrite rod 
aerial. A.G.C. counteracts fading from 
distant stations. Power comes from two 
minute pill size batteries which give 
about 70 hours working life. Plugging in 
the lightweight earpiec e switches the 
set on. 
Complete kit of parts including white 
plastic case finished in gold and black, 
lightweight earpiece, transistors, 
components and instructions. 

MALLORY MERCURY CELL ZM.3 12(2 reqd.) each l/l I: pack of 6— 10/6 




A MOST SATISFYING 
SET FOR ANYONE 
TO BUILD 



;ht earpiece switches the 

E^3 



MHMMIilfillrtiliHa 



f 9'- 1 



SPECIAL MONEY SAVING OFFER 
No. I TO P.W. READERS 

By buying a Sinclair Z.I2 Amplifier 
(See next 2 pages) with your Micro-6, 
you can save 9'- and have the basis 
of a powerful car, portable or dom- 
estic radio, bought separately, these 
items come to £7.9.0. Send now for 



EEEEa £7.0.0 




More money saving offers on next pages 
NOW REMOVED TO NEW AND LARGER PREMISES 

SINCLAIR RADIONICS LTD., SINCLAIR HOUSE 
22 NEWMARKET ROAD, CAMBRIDGE 



> 



1092 



PRACTICAL WIRELESS 



April, 1966 



SINCLAIR MICRO FM 

7 TRANSISTOR FM SUPERHET TUNER-RECEIVER 




WITH PULSE-COUNTING DETECTOR 

WITH LOW I.F. TO CUT OUT ALIGNING 

WITH 2 OUTPUTS FOR DOUBLE PURPOSE 
OPERATION 

ALL YOU WANT FROM AN FM TUNER 
AND RECEIVER IN A SINGLE UNIT 



SIZE 2*£' X 



Use it as-— 



ANF.M.TUNEtt. 
TORYOUttTAPE 

TIECORDER. 



(74x43X19 mm.) 



For far less outlay and trouble you can 
enjoy building and using the most ad- 
vanced F.N design in the world when 
you buy the Sinclair Micro FM. This 
fully-fledged 7 transistor, 2 diode FM 
superhet has original features that en- 
sure superb audio quality and great 
sensitivity together with utmost ease 
of assembly. There are two separate 
output sockets, an exclusive Sinclair 
feature which enables you to use your 
Micro FM as a tuner and as an inde- 
pendent pocket size portable receiver as 
you wish. This wonderful set is just 
about as big as a packet of 10 cigarettes 
and is as outstanding in appearance as in 
its performance. Many other excellent 
features are included in the Micro-FM 
to make building an FM set 
easy for everyone. Best of all, 
it brings first class performance ^ 

with a saving of pounds. 




ilP*' ASA TUNER. 
|1 TOB.YOUE M-H 



AS A SELF- 
CONTAINED 
POCKET F.M 
RECEIVER. 

(TAtAciy 

One OttAe 




\ Pulse counting discriminator 

Low I.F eliminates alignment problems 

Tunes from 88 to 108 Mc/c 
| Audio response— 10 to 20,000 e/« ± IdB 
| Signal to Noise ratio— 30dB at 30 

microvolts 
| Operates from standard 9V battery, 

self-contained 




Complete kit inc. telescopic 
aerial, case, aluminium front 
panel, dial earpiece, 2nd outlet 
plug and instructions. 



£5.19.6 



SPECIAL MONEY-SAVING OFFER 
No. 2 TO P.W. READERS 

To make it possible for constructors to obtain the 
best possible standards of reproduction, we are 
offering the Micro FM together with the Z.I2 
described opposite for £9.10.0 instead of the usual 
price of £10.9.0. Send now for 

EH3H £9.10-0 







* TECHNICAL DETAILS 

Seven transistor. 2 diode FM superhet for use as 
a tuoer and as a self-contained pocket receiver. 
The R.F. ampliller is followed by a self oscillat- 
ing mix er. Low l.F. dispenses with the need (or 
alignment. A 3 stage I.F. amplifier produce* * 
Bquare wave of constant voltage which in fed 
Into the pulse counting discriminator. Thl* 1= 
converted Into pulses to reproduce the original 
modulation exactly. -After equalisation, the sig- 
nal Is fed to the audio output socket and to the 
receiver's own audio amplifying stage for using 
the Micro FM as an Independent self-contained 
receiver. A.F.C. locks* on each station tunnd in. 
THE SINCLAIR MICRO FM is self-contained 
within a neat black plastic case faced by an ele-. 
gantly designed front panel of brushed and poli- 
shed aluminium with spun aluminium tuning 
dial to match. 

THE WORD'S FIRST 

POCKET-SIZE 

COMBINED FM 

TUNER — 

RECEIVER 



Guarantee 

Should you not be com- 
pletely satisfied with your 
purchase when you re- 
ceive it from us, your 
money will be refunded 
in full and at once without 
question. 



FULL SERVICE FACILITIES AVAILABLE TO ALL SINCLAIR CUSTOMERS 



NOW REMOVED TO NEW AND LARGER PREMISES 

SINCLAIR RADIONICS LTD. 

SINCLAIR HOUSE, 22 NEWMARKET ROAD, CAMBRIDGE 



April, 1966 



PRACTICAL WIRELESS 



1093 



SINCLAIR Z. 12 

COMBINED 12 WATT AMPLIFIER AND PRE-AMP 



The ultimate in 

SIZE, POWER 
QUALITY 
AND PRICE 



SIZE- y x If* x 11" (75 x 44 x 33mm.) 
12 WATTS R.M.S. (24w. PEAK) 
l5-50,000c/s 4-ldB 
IDEAL FOR 12V. OPERATION 



A 100% British 
product 




WITH THE Z.20 
THERE'S POWER 
IN PLENTY FOR 
Mono and stereo 
hi-fi systems 

Car for portable 

radion with the 

Micro-6 

Quality Radio 

with the Micro 

FM 

• 
Electric Guitar 

P. A. and Inter- 
com systems 



Never has such power and quality been contained with- 
in so compact a size as that of the Sinclair Z.I2. 
This eight transistor amplifier includes its own pre- 
amplifier designed to accept any type of input. The 
Z.I2 incorporates ultra-linear class B output in a 
circuit using special H.F. transistors to provide ex- 
ceptional performance standards. This newest Sinclair 
amplifier may be powered from any supply between 
6 and 20 volts D.C; the output can be fed directly into 
any load from 1.5 to 15 ohms. Thus the scope of the 
Z.I 2 is far greater than that of any other amplifier 
irrespective of price, making it the most versatile, 
dependable and compact audio amplifier system ever. 
The Z.I 2 is supplied ready built, tested and guaranteed, 
together with details of tone and volume control 
circuits by which input sources can be accurately 
matched to the pre-amp. 



Complete kit of 
parts with 8 tran- 
sistors, instruc- 
tions and Z.I2 
manual 



reto 



SPECIAL MONEY-SAYING OFFER NO. 3 
TO P.VY. READERS 




You can save still further by buying 
two Z. 1 2s together at the special price 
of £8.8.0 instead of the usual price of 
£8.19.0. This is a wonderful opport- 
unity to possess a low priced super 
quality stereo system. The X.I 
Power Supply Unit (£2.14.0) will 
comfortably drive two Z.I2s. Send 
now for 



PACK'C 



£8.8.0 



THE SINCLAIR GUARANTEE COVERS ALL PURCHASES 



Please note our new address 

TO WHICH ALL COMMUNICATIONS SHOULD BE SENT 



TECHNICAL DETAILS 

8 transistor hi-fi amplifier with integrated pre-amp, 

using special H.F. transistors. Generous negative 

feed-back assures superb quality. 

SIZE— 3" x IJ" x l£- (75 x 44 x 33 mm). 

WEIGHT— Three ounces. 

OUTPUT— 12 watts R.M.S. continuous sine 

wave (24w. peak). 

15 watts R.M.S. music power (30w. peak). 
FREQ. RESPONSE— 15-50,000 c's -;- IdB. 
OUTPUT IMPEDANCE— 3 to 15 ohms. Two 

3 ohm speakers may be used in parallel. 
INPUT— 2m V into 2K ohms. 
POWER REQUIREMENTS— 6-20V d.c 
SIGNAL to NOISE RATIO— better than 60dB. 
QUIESCENT CURRENT CONSTN— 15mA. 
TONE & VOLUME CONTROLS odded to 

amplifier as required. A variety of systems for mono 
and stereo are given in the manual supplied with 
every Z.I 2. 

If you do not wish to cut this page, please 
mention PW.4 when writing your order. 



ORDER HERE ! 

To SINCLAIR RADIONICS LTD., SINCLAIR HOUSE, 
22 NEWMARKET ROAD, CAMBRIDGE 

Please send goods indicated below 

ITEM QUANTITY 

Sinclair Micro-6 ... £2.19.6 

Pack 'A' £7. 0.0 

Sinclair Micro FM £5.19.6 

Pack'tV £9.10.0 

Sinclair Z.I2 ... £4.9.6 

Pack 'C £8.8.0 

Power Pack X.I ... £2.14.0 



for which I enclose Cash -Cheque! Money Order 
value £ s d. 



ADDRESS 



1094 



PRACTICAL WIRELESS CLASSIFIED ADVERTISEMENTS 



April, 1966 



SERVICE SHEETS 



SERVICE SHEETS for all makes of 
Radio and TV. 14»25-<:066. Prices from 
1/. Triitih free faULt-flrvdimg guide. 
S.AJ5. inquiries. Oa«adog'Ue of 6,000 
models 1/6. Valves, aiodaro and 
obsolete, Raddo/TV Books. S.A.E. 
lasts. HAMILTON RADIO, Western 
Road. St. Leonards, Sussex. 

SERVICE SHEETS, Radio and Tele- 
vision. 4/-, .post paid. VEST AND 
EMERY, 17 Hailgartih St., Duotoam. 

SERVICE SHEETS, Radio. TV. 5,000 
models. List 1/-. S.A.E. Inquiries, 
TELRAY, 11 Maudland Bank, Preston. 



SERVICE SHEETS (75.000), 4/- each. 
Callers -welcome. Always open. 5 
Soutii Street, Oakenshiaw. Bradford. 



SERVICE SHEETS 

4/- each, plus postage 

We have the largest display of Ser- 
vice Sheets for all makes and 
types of Radios and Televisions, 
etc., in the country. Speedy 
service. 

To obtain the Service Sheet you 
require please complete the at- 
tached coupon. 



Name: 



Address: 



To: S.P. DISTRIBUTORS 
44 Old Bond St., London, W.I 

Please supply Service Sheets for 
the following: 

Make: ______ — — , 



Model No. 

Make: 



Radio/TV, 



Model No- 
Make: _____ _ 



Radio/TV. 



Model No Radio/TV 

I require the new 1966 List of 

Service Sheets at 1/6 each plus 

postage. 

(please delete items not applicable) 

I enclose remittance of 

MAIL ORDERS ONLY Apr. PW 
SOUND RECORDINGS 



A UNIQUE TAPE BUY! Top brand 

7in„ 2,400ft. f 25/.; 5Jin., 1,200ft., 15/-.' 
P. amd p. 1 ait 2/-, 2 ait 2/9, 3-6 ait 3/6. 
B&iwalns im all sizes. S.AJ3. for Ust. 
E. C. KIKGSLEY AND CO. LTD.. 93 
Tottenham Count Road, London. W.l. 
EOS; on 6500. 



RATES: 1/8 per word (minimum 12 

words). Box No. 1/8 extra. 
Advertisements must l>c prepaid and 
addressed to Advertisement 

Manager. "Practical Wireless." 
Tower Ilouse. Southampton St., 

London W.C.2. 



RECEIVERS & COMPONENTS 



SPEAKER REPAIRS. Cones fitted. 
Satisfaction guaranteed. L. S. 
REPAIRS, Pluckley, Ashford, Kent. 



R & R RADIO & T V SERVICE 

Dept. P.W. 
MARKET STREET, BACTTP. LANGS. 
Telephone 485 
SALVAGE VALVES Tested before despatch 

SF13 4/8 TJ329 5/- PL36 8/- 20P4 6/8 
0L1S 4/8 10P14 5/- PL82 8/6 30P16 5/- 
EF80 1/8 20P6 8/6 U801 7/6 PCC84 4/- 
ECCS2 3/- 30P 7/- 10F1 1/6 PY91 8/6 
ecdso 8/6 eras 5/- 20F2 5/3 T301 6/- 
S0F5 5/- EB91 1/- 30FL1 5/- 10P13 6/8 
PL38 6/- EPS5 5/- PYS2 6/- 20D1 2/- 
PCPS0 4/- 6/30L2 4/- 6U4GT5/- 30P12 5/- 
PL81 6/- 20P3 6/- 6F1 2/6 PY83 5/- 
PZ30 5/- 30PL1 4/- EY80 4/- 
Speaken. Ex-TV. Sin. round 8 x 4in., 3/6; Sin. 
round. 6/-; post 2/-. 

Line Ootput Transformers available. State set 
model Mo. 

Turret Tuners. 8/-, post 2/-. 

Sean Coils, etc. Quote set model No. with all en- 
quiries and 8.A.E. for prompt reply. All goods 
snbject to satisfaction or money refunded. 



TAPE RECORDERS, 
TAPES, ETC. 



TAPES TO DISC — using finest 
professionail equipment — 45rpm=l8/-. 
S-A.E. leaflet. DEROY, 52 Hest BamJc 
Laoe, Lancaster. 



RELAY BARGAINS: Mod plug-nin 'type. 
4-oole c/o, 12/- P-P-, tocl. base. A. 
KNOX, 101 DaikeiHh Rd.. Bdanbuxgh. 

Assorted High Stab Resistors. 7/6. 100. 
Assorted Syflex P.F. Condensers. 7/6. 100. 

Copper Laminate Board, 12' z 12*. 5/-. 

single or double sided. 

Paxolln Sheet, 1 I, S ' x 12" x 12*. 3/«. 

Thin Paxolin Sheet, approx. 1 l tt ' x 12* x 12*. 
6 sheets for 5/-. 

White Plastic Sheet, approx X / 3S *x 6J'x 24*. 
suitable dials, insulation, case fronts, etc. 
4 sheets for 5/-. 

8mall E.M. Counters, 5 digit, 500 ohm. 6/6. 
Bulgin Extra Sensitive Mloro Switch, 5/-. 
P.O. Relay 2000 ohm. IB. 5/-. IM. IB 6/-. 

Key Switches, 4 pole. 2 throw. 3/6. 3 position 
DP+DP centre off. 5/-. 3 c/o-rl c/o centre 
off, 6/-. DP+DP 2 for 5/-. 
Pleasey Plugs and Sockets. 12 way, 3/- pr. 
6 way. 6/- pr. 

6 or 12 way screened cable to match. 3/- yd. 
Breast Mike. 6/-. Carbon Inserts, 1/6. 

Power Pack and L.F. Amplifier for 38 Set, 

15/-. 

Battery Ever-Ready. 90v+7iv. 4/6, 12 for 30/-. 

Small Component Boxes, 12/6. for 60 sample 

6d. 

Mu, Metal Screen for 5uP7 with fittings 6/6. 

250 m/a Puses U' x i'. 5/-. 100. 

100 volt Hand Generator. 7/6. 

Valves New Boxed, 6V6, 4/6. EP91. 3/-. 

6AL5. 3/- 

Rheostat WW Rotary. 15 ohms. 3.6 amp. 12/6. 

Details of Instrument Case Assembly. 

Free send large addressed envelope. 

Elac Speakers. 5*. 5/-. 7* x 4', 7/- 8'. 8/-. 

Terms Cash with Order. Post. 27- on orders 

under 20/-. 

E. R. NICHOLLS 

Mail Order and Retail Shop 
46 LOWFIEXD KOAJD 
• off SHAW HEATH. STOCKPORT 
CHESHIRE 



Test Set Type 219 

I/P 230v. 50 c/s this Is ft Pulse Generator cover- 
ing 500 c/s to 10 Kc In two ranges directly cali- 
brated. The pulse width can be adjusted to 6, 4, 
3, 2. 1 or .5 Usee, by switch on front panel, the 
O/P can be switched to +50, +10 or — lOv. 
and is variable down to 1 Mill volt, there is also 
a 20 Usee, syne. O/P pulse, it is also possible to 
obtain a 'Square wave 1 to 1 and a linear saw- 
tooth from these units, also it is possible to ex- 
tend the frequency range. These are supplied in 
good condition with leads, circuit and outer 
cover, un-tcsted. Prico £4.10.0 plus 12/6 can. 

Time Base Unit 140 

These units are sold for breakdown and contain 
the following. Valves EP91 x 6. EB91 x *. 
ECCS2 x 2, ECC83 x 2, ECC81. 8CH6 x 4, 11 
Pots W.W. type. 2 Toggle Swt.. 8 Coax Sks., 
120 Resistors including a large number of 1, 2 
* 5% types, 30 conds, 6 32-way tag boards, etc. 
Supplied in good clean condition. Price 80/- 
plos 7/6 post. Coax Plugs 1/8 each. 

Ind Unit C.R.T. 100 

This is a twin tube radar display unit with 
C.P..T.S. tvpes CV21S4 21 in.. CV2236 3iin>and 
valves EF91 x o, EB91 x 5, 12 AT 7 x 6. t 
2, oCH'i, 19AT77. CV2179. 6F33, Meter edge- 
wise reading type to 2000 yds., 1 Ma. linear 
scale also 7 relays, 20 Pots. 3in. magnifier etc. 
Supplied in good" condition in transit case. Price 
£3.17.6 plus 12/6 carriage. 

Monitor AN/GRD 

This comprises a Scope. Bearing lnd. and A.F. 
monitor. The scope uses L'.K.T. type 2BP1 and 
valves 6AU6 x2,"6ALS. 12AU7 t 2, 6AQ5 x 2. 
OA2, 2D21, 12AX7. 5Y3 x 2, also 3in . speaker 
360° Bear Ind., 4Jin. dia. controls focus, brill. 
X & Y shift, sync. gain. X amp. power I/P is 
HSv. 50 c/s, 19in. rack unit with outer cover in 
good condition with circuit. Price £5.10.0 plus 
12/6 carriage. 

Test set type 5B 

This is a battery operated crystal controlled 
signal generator covering the band 100 to 12fi 
Mc/s with modulation, there is also Meter 1 Ma. 
2jin.Fl. Rd. 3 gang 30 pf tuning cond. yai IA, 
i section Ae etc Complete in case sUe 14 x i x 
12in. with front cover. Brand new and boxed. 
Price 85/- plus 10/- carriage. 

Rx Unit Type 3582 

This Is a 5 stage 7 Mc/s I.F. strip with Det. a 
Vld. O/P a high cycle P.U. is fitted with 5U4 4 
6X5 valves, this can be removed to leave ample 
room to fit a 50 c/s P.L". These units arc a 
modem version of the 1355 Rx and the R.F. 
24/27 tuning units will ping into the trout ol 
these units. Supplied In good condition with 
circ Price 86/- plus 10/- carriage. 

Blower Motors 

I/P 115v. B0 c/s 22 watts. 3000 r.p.m., outlet 
2J x liin., Inlet ljin.. dia. overall length 5§ln. 
Black crackle finish. Brand new and boxed. 
Price 25/- plus 3/- post. 230/UBv. Anto Trs. 
8/6 post paid. 

Meters 500 U.A. 

Scaled to 5, Marconi single hole fixing type, 
aj O.8.D. 90 ohm int. res. Price 16/- plusl/6 po*. 

Selenium Rectifiers 

H.W. type I/P SOOv. O/P 100 Ma with mounting 
brackets: American manufacture. Brand new 
Price 8/8 ea. plus 1/- post or 4 for 10/- post paid. 

Coder Unit Type 51 a 

This unit contains a small enclosed 12 volt D.C. 
motor which drives Into a two stage gear box to 
give an O/P speed of 6 r.p.m.. the O/P from the 
gear box turns a disc which in turn operates MU 
of contacts. There is also control relay and valve 
on small chassis with coven in good condition. 
Price 26/- plus 4/0 poet. 

Power Unit Type 599a 

I/P 200-2S0V. 50 c/s O/Ps 12 volts D.C. at 3 
amps & SOOv. H.T. at 40 Ma as 6X8 4 P.W. 
bridge rect. Mains I/P plug* switch fitted; these 
were made to supply a number of the 51a units. 
Complete on chassis with outer cover in new 
condition. Price 42/6 pins S/6 carriage. 



B. SLATER 

34 Lifford Street 

Sheffield 9 






April, 1966 



PRACTICAL WIRELESS CLASSIFIED ADVERTISEMENTS 



1095 



RECEIVERS & COMPONENTS 

(continued) 

TRANSISTORS, UNMARKED. UN- 
TESTED. 40 for 10/-. p. and p. 1,'-, 
4 packets post free. Relays, thousands 
i », special catalogue free. 
General catalogue of Mecftwwiiical and 
al Gear. Tools, ©to. (5.000 
items), free. K. R. WHISTON (Dept. 
PRW i, New MlMs. Stockport. 



TV CHASSIS. 110. with v,h.f.. store 
soiled. £5 including carriage. NEW 
ran. TUBES with sniaiK spot bums, 
£4 incrudln* carriage. C.W.O. TRURO 
VALVE SUPPLY LTD.. Carclew «... 
Truro. Cornwall. 




"HEATHKITS" can now be seen in 
London and purchased on easv 
u-rm.i. Pree broohuire. direct tv 
REPLACEMENTS LTD.. Deipl. PW7-9, 
126 Hani' j. ton Road. West Norwood, 
S.E.27. G-IFsy Hill 8166. 

MARCONI CANADIAN RECEIVER No. 52 

Shipping 
AmalHiir, 
a Broad- 
cast. 3IaK- 
ulficent 1«- 
nM '■■■ 
earner in 
lhrt« nrit> 

ehed »..>. 
hand- cov- 
ering 1.7fi- 
I 6 M . , • 
(19 - 170 
metres). 
Mill 
valve cry- 
stal cali- 
brator, employing dual crystal to provide marker 
eheok at lii-iuii-foOO kc.'n. One Ktf and two IP 
Other refinement*: valve. HT. and Signal 
-nud ,'iln. speaker and 
• ith switched control. RK-AF 
- Umiter, Filt.-r. I'.FO. Heterodyne piiih 
oontmL Wide and Narrow Bandwidth Man. or 
H I RT. l-'a-i and Wow Inuing with look. 
"s' 1 Tuning (plus ti minus). BlK 
"' working. A.C. 
Mmoj MO/SeOr. tit. Carr. «. 

No. 68 GROOLD-STATION comprising Receiver. 
Tranimitler and l-'v. D.C. Power Unit. 42710 0. 
Our, t-.'.jo.o. ^Mainland only). 

NATIONAL H.R.O. SENIOR RECEIVERS 5T 
MODEL 

at i- lad 
onodltlon. Beoeiver 

only £18.10.0. set ol 
4 coils. £6.0.0, car- 
riage 30 -. Power 
I'nit. £2.15.0, our. 

10-. 

4 VALVE 4 WATT AMPLIFIER 

i' 1 ' fJora trantdhrruero 
A.C. Main' 1 10/230 ralta 
DM ohm- of high Imped- 
ance input. Output :; .r 
•100 ohm' 

Control-: tin, Oil sw it.li 
OM0 control. Indicator 
tlon panel. 19 x 7 x 7in. Brand 
irton. 79/6. Carr. 10/-. 

TELESCOPIC AERIAL MASTS. Tubular steel 

ropperised. spray finish, ring cam locking on each 

:'"r full or any height required. 

Suitalile all HxlngH and l,a»e locations. Bottom 

Mt, (4 section) Closed sit. 

.-,-.: HiH,. 55/-. fair. 8/-. 34fl. I 

Bin. Weight •_iilb. 76/-. Carr. «/-. 
Further height by adding S-4(t. Whip ncctlouo 13/6, 
Our, 4/-. Special price for quai 

ROTARY TRANSFORMER. 12v. B.C. Input. 2.',0v. 
li.''. output ui lii niA. Sl»* Si x Jin. Brand new 
17/8. F. « i". 0.-. 

R.F. ANTENNA TUNER (A.T.TJ.) Calibrated scale. 
Ideal 1«0'$0'40 metres. Limited number nnlv. 

Bond new with hjstraoUotu, 17/6. p. 4 p. 7/a. 
liet 01 other bargains 1/.. S.A.E. all 
Crc.nt Terms Available. 

A. J. THOMPSON (Dept P.W.) 

"EILINO LODQE" 

C0DIC0TE. HITCHIN. HERTS. 

Phone: CODICOTE 242 




BUILD 

24 INTERESTING 

DESIGNS 

with your own components and tran- 
sistors on a printed-elrcult chassis. 

"EXPERIMENTAL" 

PRINTED CIRCUIT KIT 

Contents 

(11 2 Copper Laminate Boards 4J* x 2t*. 

(2) Resist. <3)Etchant.t4)ResistSolverit. 

(5) Cleanser/Degreaser. 

(6) 16-page illustrated booklet. 

"PRINTED CIRCUITS FOR 

AMATEURS" 

containing- full etching Instructions. 

(7) Attractive case 4}' x 21' for a pocket 
Transistor Radio. Crystal Set. etc. 
Suits designs, enclosed. 

18) Miniature Radio thai MW/LW. 

(9) Miniature Radio Dial SW/MW/I.W. 

Also free with every kit. 

'10) Essential Design Data and Con- 
structional Details of easy-to-bulld. 

24 SUGGESTED PROJECTS 

which you can build on a P.C. chassis 
made from this kit. Part Lavouts. 
Circuit Diagrams. P.C. Chassis plans. 
Assembly Drawings. Photographs. Many 
recently developed very efficient designs 
you probably haven't heard of vet. 
(1> Crystal set with biased detector. 
(2) Crystal Mt with voltage-quadrupler 
detector. (3) Crystal set with dynamic 
loudspeaker. (4> Crystal tuner with 
audio amplifier. (5) Carrier Power Con- 
version Receiver uses the B.B.C. signal 
to bring in distant lorelgn stations. No 
battery. (6> Split-Load Neutralised 
Double Reflex Pocket Loudspeaker Re- 
ceiver. Uses only 3 transistors In a very 
sensitive and economical circuit. <.7> 
Matchbox or Photocell Radio. Small 
receiver powered by a single photocell 
or mercury batterv. (8) "T3IFLEXON" 
Triple Reflex with sell-adlusting regen- 
eration, varlttble bandwidth, amplified 
A.Ci.C. Uses only 3 transistors In cas- 
cade. Each transistor amplifies 3 times. 
ferrlhV gain. Excellent selectivity. 
The best circuit yet invented (Patent 
Pending). Simplicity or the TRF with 
the perloimutii-pu! " thesuperhet. Makes 
possible tho construction of extremelv 
low-consumption submlniature radios, 
iso Solar Battery Loudspeaker Radio. 
Lmplovs photocells to charge a small 
accumulator. Entirely practical cesign. 

3 SCBMIMATVRE RADIO 
KKCKIVKILS 

The smallest 3 designs yet offered to the 
Home Constructor anywhere In the 
world. Based on the "Trlflexon" circuit. 
Let us know If you know of a smaller 
design published anywhere. (101 Post- 
age-stamp Radio. Size only 1.62' x .95' x 
.25". (11) Wrist-watch Radio. 1.15' x 
.80' x .55'. (12) Ring-Radio. .70' x .70' X 
.5o'. (13) Bacteria-powered Radio. Runs 
on sugar or bread. (14) Radio Control 
Reoeiver. (15) Transistor P/P amplifier. 
(16) Intercom. (17) 1-valve amplifier. 
U8> Photoelectric Burglar Alarm, '1S« 
Light-Seeking Animal. Guided Missile. 
(20) •■Perpetual Motion" Machine. 
Atmospheric Engine. (21) Metal Detec- 
tor. (22) Simplo Transistor Tester. (23) 
Human Body Radiation Detector. (24) 
Electronic Man/Woman Discriminator. 
Thermal Proximity Fuse. etc. 
P.C. Kit price 7/6. Post and pack. 1/-. 
Extra coppor laminate aval lable. 

"YORK ELECTRICS" 
I8la, York Road, 
London, S.W.I I. 

Send S.A.E. for full details 



RECEIVERS & COMPONENTS 

(continued) 



19 SETS (A sets complete I with 
Power Packs, Con-ro: Box and all 
Connectors, tested and working R 
and T, £6 '10 - plus 35 - carriage and 
packing. Sets onlv, £4, 20/- c and 
p. Head Sets £1. 46 SETS, new, 
unpacked, complete with 2 Head 
Sets. Connectors. Havrrs.tri-c. £6/10/-. 
• 17/6. WALDEN, Main Road 
Garage, Sou/tfa Gtreen, BiMertcay, 
Essex. 

RADIO-TV-ELECTRONIC 

COMPONENTS 

Bargain Prices 

NEW TRANSISTORS 
OC44. OC4D, OC71, 0(.'72, OCX I m. OCSIdm, AF117 
„_ 2/8 each. 

BY100. 500m,'a8/- each. Iron Dust Cores Jin. 1/- doa. 
BSa i^.v- Losa Vaii.- Balden, 1/6 do*. 4 pole .1- way 
Rotary Switches 1/6 each. Fa.\ Panel* 6 x 41n. lOd. 
each. Miniature Condensers 4raf, Bmf, niini, 90mfc 
BOmf, lliomf. 15 vw. all 1/4 each. -1 Condi -n-cis HOOv. 
1/- «-aeh. .Miniature. 001, DOS. 008, OB, OS, 100 vw. 
6d.-a.-h. a.', mi, 86 vw 1/6 each. PP3 Batten i lip, 
nth i--i*,l- 1/- each, Small loatnimeBl Sen v»,irivers 
6d. eaob, Bmall Soldering iron- 240v. SO »ati 10/- 
r- SIS v». 8d, each. Edgewise 
Xuiuin, OoBtHb ,1., Hith switch, Jap replaoanwat 
3/6. Berrlc* aheeu 3/- aaea. F-. * p, BU plaiiga, 

Maintenor Radio 

222 GREAT WEST ROAD 
HOUNSLOW, MIDDLESEX 

SILICON PLANAR Transistors. 18V. 
200-nW. :00mA max.. fl=,lS0 to 300. 
NPN at 5/S, PNip at 7/-. Brand new. 
■•By Return" serv<oe ELECTRO^ 
VALUE, 6 MansfiFld Piace, At 
Berksiiir^. 

PATTRICK a KINNIE 

81 P»rk Lane, Hornchurch, Essex. 
ROmford 44473. 
HIGH SPEED MAGNETIC COUN- 
TERS (4xlxlin.) 6/I2/24V. (state wh.ch). 
4'6 ea. P. & P. I/-. 

SANGAMO GEARED MOTORS. 

I R.P.M, 240v. 27'6 each. 

40 WATT POWER AMPLIFIERS 

(E.M.I, new boxed). 2 x Kt66 4 x EF37A. 

£11.10.0. P. & P. 15 -. 

FIELD TELEPHONES TYPE "F" 

(mint condition). 70'- per pair. P. & P. |0/-. 

TELEPHONE HANDSETS (latest type) 
smoke grey 10'- each. P. & P. 2/6. 
AMPLIFIED TELEPHONE HAND- 
SETS. Built-in transistor amplifier and 
volume control. Red, ivory, green, black. 
35'- each. P. & P. 2 6. 

BULK COMPONENT PARCELS 

'00 capacitors (latest types) SO pf to -lixf. 
250 carbon resistors 4 and 1 watt transistor 
type. 

250 carbon resistors i and I watt (all 5% to 

ISO hi-stab resistors i, I and 2 watt. 
Exceptionally varied assortment any parcel 
10'-. P. & P. inc. 

3000 TYPE RELAYS. I0for25'-. P.& P.2/6. 
ELECTRIC CHECK METERS (mint 
condition). 40 amp. 20'- each. P. & P. 5/.. 

1st GRADE TRANSISTORS. OC. 23 28/ 
35 36. 10'- each. OC. 42/44, 45 7 1 72, 75/76/ 
7781 8ID 3'- each. OC. 170 4'6 each 
AC. 128 4'6 each. 
SAVBIT. 18 S.W.G. SOLDER. ±lb V6. 

HEADSET & MIC MOVING COIL. 
10'- Set P. & P. 2/6 

DLR5 HEADPHONES. T6 pair. P. & P. 

1/6. 

QUARTZ CRYSTALS (glass encapsul- 
ated) 87G base 9.999 Kc/» or 32 Kc/s. 
10'- each. P. & P. |/6. 






1096 



PRACTICAL WIRELESS CLASSIFIED ADVERTISEMENTS 



April, 1966 



RECEIVERS & COMPONENTS 

(continued) 



SHORT OF MONEY? Turn your 
Relays and Contacts <into cash. S.A.E. 
for details. 112 Groby Road. Glen- 
field. Leicester 



4tiA RADIO; 



CANADIAN MARCONI 52 RECEIVERS 

1.75 to 16 Mc/s as previous adverts. £10.10.0 
or with ZE1Z Power unit for 230v. A.C. 
£13.10.0, both carriage paid. Handbooks 
with circuit. 5/-. leaflet S.A.E. 
LOUDSPEAKERS lOin. 3 ohm in wood 
case. Case soiled, 600 ohm Line Transformer. 
25/- carriage paid. 
CERAMIC Insulated 3 gang variables, 56 x 

56 x 35 pF. 3/6. post 1/6. 

POCKET WATCHES Ex-Government 15 

Jewel Swiss movements. 50/- plus Keg'd. 

Post. 2/6. 

(Carriage charges apply to England and Wales 

only). 

Telephone: Worthing 9097 



.40/42 PORTLAND 
ROAD. WORTHING 



FOR SALE 



MORSE ^IFy 5 ! 

Tine Famous RHYTHM RECORDED 
COURSE cuts the practise tame down 
to an a-bsoluite jm-iniinAum. 

One student, aged 20, took only 13 
DAYS, and another, aged 71, took 
oniiy 6 WEEKS to obtain, a G.P.O. 
Pass Certificate, if you wash to read 
Morse easily and naturally please 
enclose 8d. in stamps or two initer- 
niatiiomai reply couipons for fiull 
explamaitony leaflet to 
G3CHS, 15 Green In., Purley, Surrey. 



240»« ELECTRIC POWERfiUIg 



mSm from I2 CAR BATTERY 



n"_ 



<** American DYHAMOTOR UNIT 

IIHt12i.0lltll2W25lt.il ISO to2M«ltt!. 

hrltel Itr iiimsmi. ro«« "Wis "< '-' 
niwnUC/K iitcniui muirMi«T -hi 
ntHrlil unllirria 0MY/ll«ieMe:ireri 
Suit llnpU liillopi In full IJislrjiHl (Mill 
Bill. saimiHcniwicis.cuviiits. 
■ w 




SPECIAL OFFER 

GEVAERT TAPE. New, Boxed, 5f, 
600ft. with Stop and Leader Tapes, 9/- 
or 6 for 50/- post paid. 
GRUNDIG MAI 2 Transistor Pre-amps 
for Tape Monitoring or Microphone 
Boosters, 57/6 post paid. 

LIST PRICE 4 GNS. 

LEE ELECTRONICS 

400 Edgware Road, Paddington 5521 

Send for Free Lists and details of above 



FOR SALE 

(continued) 



ELECTRIC SOLDERING-IRON 

FANTASTIC 
BARGAIN OFFER 

Lightweight Pistol Grip handl 
40 watt. 240/250V. A.C Solid 
copper bit. Detachable handle 
forms cover for iron when not in 
use. With 4jft. Safety 3-core 
flex. Indispensable for 
every home handy- 0>L¥ 
man. A boon to model 
makers and a necessity 
for every wireless en- 
thusiast. Offered to P & P 
you at this new amaz- 1/- 
ing price. 

C. H. SERVICE (Dept. P.W.) 

Lusted Hall Lane, Tatsileld, Kent. 




SPECIAL OFFER 

I watt S.T.C. 300 mc/s N.P.N. 
Silicon Planar, 100% Transistors 
limited stocks. £1 for 6. 



3/- each. OC44, OC45, OC70, 
OC7I, OC8I, OC8ID, OC200, 
GET 1 6, GET20. 

41- each. AFII4, AFII5, AFII6, 
AFII7. OCI70.OCI7I. 

5'- each. OCI39, OCI40, GET7, 
GET8, GET9, EXI4I, BY 100, 
OA2II. 



SUN SOLAR CELL KITS 

24 page Booklet on Experiments 
inc. 4 Sun Solar Cells II'- set. 

G.P.O. DIAL TELEPHONES 

20'- each. 35'- pair. 

Send 6d. for full lists: — 
inc., S.C.R., Zeners. 

CURSONS 

78 BROAD STREET 
CANTERBURY, KENT 






GET THIS AIR DRYING 
HAMMER FINISH NOW. 

So Provisional . . . the YDKAN aeroiol war/I 

YTJKAN Aerosol spravklt contains 16 ozs. fine quality, durable, easy Instant spray. 
No stove baking required. Available to Grey, Blue. Gold. Bronze at 14/11 at . our 
counter or 15/11, carriage paid, per pushbutton self-spray can. SPECIAL. u"n«. 
1 can plus optional transferable anap-on trigger handle (value 0/-) lor 18/11, carr. pa. 
Choice of 13 sell-spray plain colours and primer (motor car quality) also available. 

YU KAN Che - 6 " ~ "*" --- "°-~- »-■ • -*- w ■ <0pen -- * 




FOR SALE 

(continued) 



ITAMMEKITE 

HAMMER PATTERN BRUSH FAINT FOB 

PANELS AND BOXES 

■* THE PATTERN IS IN THE TIN * 

ALL YOC DO IS BRUSH IT ONI 

2J oz. tins 8/6 i gallon 85/-* 

iplnl 7/6 1 gallon 58/-* 

1 pint 15/- ('sent by road) 

Carriage: Orders up to B/-. 9d; up to 10/- 1/9; 

over 10/- 8/9. 

Colours: Blue, Silver or Metallic Black. 

Return of post service, Mon. to Fri. 
From your component shop or direct from the 
manufacturer: 

FINNIQAN SPECIALITY PAINTS (PW> 

Mickley Square, Stocksfield. Northumberland 

Phone: Stocksfield 2-280 



WANTED 



WE BUY New Valves and Transis- 
tors. State price. A.D.A. MANU- 
FACTURING CO., 0il6 Alrfreton Road, 

NoUdnglhara. 

URGENTLY WANTED: New, Modern 
Valves, Transistors, Radios. Cameras. 
Tape Recorders and Tapes. Watches. 
Tools, any quantity. S. N. WILLETTS. 
:€ New Street. West Bronwnoh. 
Staffs. Tel. 2392. • ' 

DAMAGED AVO METERS wanted. 

Models 7 and 8. Any condition. Any 
quantity. HUGGETTS LTD., 2-4 
Paiwson's Road, West Croydon, 



WANTED 
VALVES ONLY 

Must be new and boxed 
Payment by return 

WILLIAM CARVIS LTD. 

103 North Street, Leeds 7 



WANTED: Popular Brand New 
Valves. R.H.S.. Stamford House. 538 
Great Horton Road, Bradford"?. 

WE BUY New Vaitoes lor cash, large 
or small quantities, old types or the 
latest. Send details. Quotations 
by return. WALTON'S WIRELES& 
STORES, 15 Church Street, Wolver- 
hampton. 



MISCELLANEOUS 



Dept. P.W./4 307a Edgware Rd.. London, VV.2. 



Closed Tours, afternoon). 



CONVERT ANY TV SET into an 

Oscilloscope. Diagrams and instruc- 
tions 12/6. REDMOND, 42 Dean 
Close, Portslade, Sussex. 

— ELECTRONIC MUSIC?— 

Then how about making yourself an 
electric organ? Constructional data 
available— full circuits, drawings and 
notes! It has 5 octaves. 2 manuals and 

Sedals with 24 stops— uses 41 valves, 
nth its variable attack you can play 
Classics and Swing. 

Write NOW for free leaflet and further 
details to C. & S., 20 Maude Street, 
Darlington, Durham. Send 3d. stamp. 



METAL WORK 



METAL WORK: All types cabinets, 
chassis racks, etc., to your specifica- 
tions. PHTLPOTTS METAL WORKS 
LTD., Ohapimaa St., Loughborough, 



April, 1966 



PRACTICAL WIRELESS CLASSIFIED ADVERTISEMENTS 



1097 



BOOKS & PUBLICATIONS 



SURPLUS HANDBOOKS 

19 set Instruction Handbook . . 3/6 P.P. Si. 
1155 Instruction Handbook . , 4/8 P.P. 6d. 
H.E.O. [infraction Handbook 3/6 P.P. 6d. 

6£ set I n*t ruction Handbook . . 6/- P.P. Od. 
38 set Instruction Handbook . . 3/6 PJ". 6d. 
46 set Walkie-talkie circuit * . 

notes 8/8 P.P. 6d. 

88 set Walkie-talkie Instruction 

Handbook 5/- P.P. 6d. 

Frefjuenor Meter BC221 Instruc- 
tion Handbook . . 3/6 P.P. 8d. 
Wavemeter Clan D Handbook 

Mk. I, II, III 8/6 P.P. fld. 

18 set Circuit Detail* 4 Note* 3/6 P.P. 3d. 

A.R.8SD Instruction Handbook 16/- P.P. I'M. 
R.107 In (traction Handbook . . 5/- P.P. fid. 
CE.100 B.83 Receiver Handbook 8/8 P.P. Bd. 
R1116 A Circuit Diagram 4 

ttatjtfta 1/9 P.P. 6d. 

R1224 A Circuit Diagram * 

Detail. 1/6 P.P. Bd. 

R1355 Circuit Diagram 4 Details 1/6 P.P. 6d. 
RP 24. 85, 86 Circuit Diagram*. 

* Detail. 1/6 P.P. Od. 

Amplinor A1134 Circuit Diagram 

<S Details 1/9 P.P. 6d. 

Transmitter T1164 Circuit 

Diagram A Details tall models) 2/- P.P. 8d. 
Resistor Colour Oode Indicator.. 

Indicate, the value of a rotator 

at a glance 1/6 P.P. 6d. 

All mall orders to: 

Instructional Handbook 
Supplies 

Dept. PW. Talbot House. 2S Talbot Gardens 
Rouudhay. Leeds, 8 



EDUCATIONAL 

(continued) 



RADIO OFFICERS' Training Courses. 
Write Principal. Newport and Mon- 
mou'-nshare College of Technology. 



TRAIN FOR SUCCESS 
WITH ICS 



Study at home for a progressive 
post in Radio, TV and Electro- 
nics. Expert tuition for I.E.R.E., 
City & Guilds (Telecoms and 
Radio Amateurs') R.T.E.B., 
etc. Many unique diploma 
courses incl. Colour TV, Elec- 
tronics, Telemetry & Com- 
puters. Also self-build kit 
courses — valve and transistor. 

Write for FREE prospectus ami find out 
how ICS can help you in your career. 

ICS, DEPT. 541 PARKGATE ROAD, 
LONDON, S.W. II. 



SITUATIONS VACANT 



EDUCATIONAL 



RADIO OFFICERS see the world! 
Sea-going and shore appointments. 
Trainee vacancies during 1966-67 
Qramts available. Day and Boarding 
.students. Stamp for prospectus Wire- 
less College, Colwyn Bay. 



CITY AND GUILDS (Electrical, etc.) 
on " Satisfaction or refund of fee " 
terms. Thousands of passes. For 
net ails of modern courses In all 
branches of Electrical Engineering, 
H BctroDuCs. Radio, TV. Automation, 
etc.. send for 166-page handbook— 
FREE BJ.E.T. iDept '.68K), 29 
Wrights Lane, London, W.8. 



TV AND RADIO: A.M.I.E.R.E.. City 
a.nd Guilds. R.T.E.B. Cert., etc.. oh 
'• Satisfaction or refund of fee" 
terms Thousands of passes. For 
details of Exams, and Home-training 
Courses (including practical appara- 
tus) in all branches of Radio. TV 
and Electronics write for 156-paje 
handbook — FREE. B.I.E.T. (Dept. 
137K), 29 Wright's Lane, London. 
W.S. 

RADIO AND TV Exam, and Courses 
ay Britain's finest Home-study School. 
Coaching for Brit.I.R.E.. Citv and 
Guclds Amateur's Licence. R.T.E.B.. 
P.M.G Cert., etc. FREE brochure 
from BRITISH NATIONAL RADIO 
SCHOOL. Russell Street. Reading 



A FULL-TIME TECHNICAL EXPERI- 
ENCED SALESMAN requ.r-d !ur 
Retail Sales. Write, giving full 
details of age. previous exoerlence 
.md A.i!..ry required, lo the Manage.-. 
HENRYS RADIO LTD.. 38 Edgware 
Road London, W.2. 



City and County of Bristol 
BRISTOL TECHNICAL COLLEGE 

Principal: E. Poole, B.Sc.Eng., M.I.Mech.E., M.I. Prod. E. 

CAREERS IN RADIO & RADAR 

Marine Radio Officers 
2-year full-time course for young 
men aged 16 upwards, leading to 
1st and 2nd class P.M.G. Certifi- 
cates and B.O.T. Radar Mainten- 
ance Certificate. 

Conversion Course (2nd class to 
1st class). 

R.T. Courses (for Full or Restrict- 
ed Licence). 

Training given on the latest types of Marine and Aircraft Equipment 
in newly equipped Laboratories at 

THE SCHOOL OF MARINE RADIO & RADAR 



Licensed Aircraft Radio 
Engineers 
2-year, full-time course for 
A.R.M.E. Licences, categories A & 
B, and 6-months courses for 
Radar Rating in association with 
the above. 



For details write to: 



Senior Lecturer: F. E. BARLTROP 

THE REGISTRAR 

BRISTOL TECHNICAL COLLEGE 
ASHLEY DOWN, BRISTOL 7 



SITUATIONS VACANT 

(continued) 



A. M.I.Mech.E., A.M.I.E.R.E.. City and 
Gi:,cs G.C.E., etc Become a Te.h- 
nician or Technologist for high pay 
and security. Thousands of pass:s. 
For details of Exams, and Courses In 
all branches of Engineering. Bu 
Electronics, etc.. write for 156-pa." e 
handbook — FREE. B.I.E.T (Dcrtit 
laSK). London, W.8 

RADIO TECHNICIAN with a sound 
knowledge of at least three of the 
fol.owlmg types of equipment is 
required immediately for Meteoro- 
logical Office Ocean Weather Ships: 
S-ngle Side-band Transmitter. Radar 
(Navigational), Radar Height Find- 
ing. Echo Sounders and Radio 
Receivers. Automatic D.F., V.H.F 
and M.F. Low Voltage Servo 
Recorders, Digital Telemetering 
Equipment. Salary scale £678-£u . 1 04 
per annum according to age, pus 
£120 per annum overtime allowance 
Free food and accommodation pro- 
vided on board ship. Applicants 
must be natural born British SUtf 
Jects. Full details from Shore 
Captain, Ocean Weather Ship Base. 
Great Harbour, Greenock. Telephone 
Greenock 24291. 



A book for every enthusiast . . . 



TRANSISTOR 
POCKET BOOK 

by «. C. Hibberd, B.Sc, M.I.E.E., 

Sen. M.I.E.E.E. 
A comprehensive guide to the char- 
acteristics and use of the various types 
of transistor now available. The manu- 
facture of the various types of cran- 
sistor. up to and including the latest 
epitaxial planar, field of effect and metal- 
oxide silicon transistors, is described 
in detail in order to make clear the 
different characteristics of each. In- 
cludes notes on the use and handling 
of transistors, and chapters on solid 
state circuit techniques and recent 
developments. 

304 pages 250 illustrations 2Ss. 

from your Bookseller, or in case of difficulty, 
27s. from C. NEWNES LTD., 
SOUTHAMPTON STREET, W.C.2. 



NEWNES 




The Famous 
E2A COMPASS 



as in current use 
in Jet Aircraft 



This compass which In tmerl on Direction Fimlcr 
ir,r "mail craft, (see article In Practical Wire 1cm 
July 1900) is also ideal for Yachts and cam. 
Jiotcd for IU awurauy and steadiness under all 
conditions, with vertical card pre»entatlon and 
calibrated every 10 degrees. Liquid Oiled and 
gives a direct reading at any angle. Jluill-ln 
correctors pnnide correction for nil cilfUilmH 
B A C. Very popular with gliding entr. 
and motorists. Cost the C kna t um enl Orel tl" 
Our PRICE ONLY £8.17.6. PIP. -JIM. 
Spring Catalogue now available tree. Top quality 
watches, stopwatches. Blnooulan, Telescopes etc, 
Send 6d. pottage. 

UNITED TECHNICAL SUPPLIES LTD. 

Dept. PW.^9. Tottenham Court Road. 
London. W.l, Telephone: Laagham 1116/7 



1098 



PRACTICAL WIRELESS 



April, 1966 



BARGAIN OFFER CORNER 

MAINS TRANSFORMERS 

Semi-shrouded drop thro' typo. Pri. 200. S20. 
240v. Sec 2S0v. J wave at 70mA and 6.3v. at 2 
amp. c.'t. 
Stock size 3 x 2j i l}lu. 1 1 l_ 

PRICE 1*/" P. 4 P. 3/-. 
PRECISION 6-MINUTE DELAY ACTION SWITCH 
Clockwork actuated. Made by Smiths. Separate 
switching actions at Intervals op to 6 mins. Each 
switch action designed (or current loading up to 15 
amps, at 250 volts. Suitable for photographic timer, 
sequence switching operations, etc. etc. Brand new 
and unused units offered at a fraction of their true 
value. OUR PRICE ONLY 10/- each. P. & P. 1/6. 
(3 or more post free). Special quotations for quantity. 
HEAVY DDTY NON-INDUCTIVE D/T MICRO 
SWITCH. Conservatively rated 10 amps at 250v. 
Standard one-bole fixing. Body size 18 x } x lln. deep 
Inc. terminal* 8/- each. P. & P. 1/- (6 or more post 
free). 

NEON A.C. MAINS INDICATOR. For panel mount- 
ing, cut out size 1} x i x Jin. deep inc. terminal. 
White case with lens giving brighter light. For mains 
200/250V. 8/8 each P.P. 6d. (6 or more post free). 
VYNADt AND REXINE SPEAKER AND CABLVET 
FABRICS. Approx. 641n. wide. Usually 85/- yard. 
OUR PRICE 13/6 per yard length. P. & P- 2/6 (min. 
one yd.) S.A.E. for samples. 
ACOS CRYSTAL MIKES. High imp. For desk or 

hand v a. High sensitivity 18/8. P. 4 P. 1/8. 

TSL CRYSTAL STICK MTKE Listed at 46/-, OUR 

PRICE 18/6. P. * P. 1/6. „ „„_ 

T.O.C. SUPPRESSOR CONDENSERS. 250v. A.C. .005 

-r .005 x .1 In tubular can }in. long x Jin. dla. 2 for 

3/-, po^t free. 

TRANSISTOR DRIVER and O/P TRANSFORMERS. 

(Tapped 3 ohm and 15 ohm output). Plus 4 suitable 

Transistors giving approx. 1 watt output 25/-. 

P. & P. 2/6. 

2-GANG .0005 TUNING CONDENSERS. 2 Sin. h. x 

2iin- d. x ljln. w. with built-in trimmer. 4/8, P. S P. 

MATCHED PAIR OF 2i WATT TRANSISTOR 
DRIVER AND OUTPUT TRANSFORMERS. Htack 
size 1 J x 1 i x Sin. Output trans, tapped for 8 and lo 
ohm output, 10/- pair. P. 4 P. 2/-. 
BRAND NEW PLESSEY. 12v. 4-pin non-sync 
vibrators. Type 12 1.48D. ONLY 8/6, P. & P. 1/6 ea. 
TWIN TELESCOPIC AERIAL. Comprising two 
3-section heavily chromed rods. Closed 12ln. each 
extending to 32in. Completely adjustable from 
vertical to horizontal. Supplied complete with uni- 
versal mounting bracket, coax lead and plug. 
Suitable for F.M. or TV. 12/6. P. Si P. 2/-. _.„„ 
4-WAY NON-TANGLE TELEPHONE CABLE. 
Latest spring back coll type, extends 121n. to oft. 
Complete with rubber bushes, 4/8 each. P. * P. I/O. 



SPECIAL BRAND NEW 
TRANSISTOR BARGAINS 

GBT 15 (Matched Pair) 16/-. V15/10p, 10/-; OC71 

J/-: OC76 6/-; AF117 7/6. „ „ 

Bet of Milliard 6 transistors OC44, 2— OC45 OC81D 
matched pair OC81 26/-. ORP12 Cadmium Sulphide 
Cell 10/6. 

EDISWAN MAZDA 
PXA101 6/6: XA103 6/6. _ „„..„.,_ 

R.F.I. Pack: 1— PXA102 Mixer; 2— PXA101 I.F. 

Amp. (Equlv. OC44 and OC45) 10/6 

R.F. 2 Pack: 2— PXA101 LP. 1— PXA102 Osc. 

1— PXA102 Mixer 12/8 

L.F.6 Pack: Consisting of PXB113 Driver Matched 
pair PX171 mounted complete with heat sinks 

(Equlv. OC81D and 0C81) 18/8 

ALL TRANSISTORS POST FREE. 



4-SPEED PLAYER UNIT BARGAINS 

All Brand New in Maker's Original Packing 
SINGLE PLAYERS 
GARRARD SP25 Do Luxe. . . .£18.10.6, Carr. 5/0 
B.S.R. GD7 with unit mounted pick-up arm. 

£4.18.8. Carr. 6/6 
E.M.I. with unit mounted pick-up arm. 

£4. 9.6. Carr. 5/6 
AUTO CHANCERS 
LATEST B.S.R. UA25 Supe> Slim mono. £6.8.6 
B.SJL UA15, £6.19.6: B.S.R. UA16. £6.19.8 

GARRARD AT6 £9.10.0 Carr. 6/6 on each. 

All the above units are complete with t/o mono 
head and sapphire stylli or can be supplied with 
compatible stereo head for 12/0 extra. 

SPECIAL OFFER 
of the famous COLLARO STUDIO 
4-speed Semi Transcription Auto 
Changer Units. 200/250v. A.C. Really 
heavy duty motor and robust mechanism. 
Designed and built for life long service. 
Stereo wired. Supplied complete with 
mono cartridge and stylii. Offered at Bar- 
gain Price of £5.12.6. Carr. 7'6. Stereo 
version £6.12.6. ALSO small number of 
GARRARD Autoslim Changers, with 
plug-in head complete with Mono cart- 
ridge. To clear at £5.10.0 each or with 
Stereo cartridge I2'6 extra. Carr. 6'6. 



SPECIAL OFFER OF LEADING 
HI-FI MANUFACTURERS SURPLUS! 

7-10 watt OUTPUT TRANSFORMERS to match pair 
of ECLS6's in push-pull to 3 ohm outpnt. ONLY 11/- 

7-10 watt" ULTRA LINEAR OUTPUT TRANSFORM- 
ERS to match pair of EC182's In push-pull to 3 ohm 
output. ONLY 15/-, P. & P. 2/6. __ 

SPECIAL MAINS TRANSFORMERS to match either 
of the above. Tapped primary. Secondary 250v. 
80mA half wave and 8.3v. 2 amps. ONLY 12/8, 
P. * P. 8/6. 



NEW CARTRIDGE BARGAINS 

RONETTE STEREO 105 CARTRIDGE. Stereo/IP/ 
7S Complete with two sapphires. Original iat 
price 67/9. OUR PRICE 24/-. P. & P. 1/-. 
ACOS GP67— 1 Mono complete. List price £1.1.0. 
Our price 13/6. P. 4 P. 1/-. 



STEREO AMPLIFIERS 

Incorporating 9 BCL83*a and 1 EZSO heavy duty 
double-wound mains transformer. Outpnt 4 watts 
per channel. Full tone and volume controls. Abso- 
lutely complete. 



3 VALVE AUDIO AMPLIFIER 
MODEL HA34 

Designed for HI-FI 
reproduction of 

records A.C. Mains 
operation. Ready 
built on plated 
heavy gauge metal 
chassis size 7{in. 
w. x 4in. d. x 4Jin. h. 
Incorporates ECC3S 
EL84, EZ80 valves. 
Heavy duty double- 
wound mains transformer and output transformer 
matched for 3 ohm speaker, separate Baas. Treble 
and volume controls. Negative feedback line 
Output 4J watts. Front panel can be detached 
and leads extended for remote mounting of con- 
trols. The HA34 has been specially designed for us 
and our quantity order enables us to otter them 
complete with knobs, valves CA K t\ p * *■ 
etc wired and tested for onlyi «"«»»•»» 6/- 




SPECIAL HARVERSON OFFER ! ! I 

BRAND NEW HEAVY DUTY 12in. SPEAKERS 
Response 45 c/s-13 Ko/s. ljin. voice coll. Available 
in 3 or 15 ohms. Guaranteed full 15 watts British 
rating. Heavy cast aluminium frame. These are 
current production by world famous maker and as 
they are offered well below list price we are not 
permitted to disclose the name. LIMITED NUM- 
BER ONLY. UNREPEATABLE at 89/6, P. * P. 
6/-. Also 25 watt Guitar Model available at £5.5.0. 
And 35 watt Guitar Model £8.8.0. 

BRAND NEW 3 OHM SPEAKERS 

5in., 12/6; 6,in., 15/-; Sin., 21/-; lOin. 26/-; 121?., 
27/8; (121n. 15 ohm 30/-) lOin. x 6in., 28/-. E.M.L 
134 x 8in. with high flux ceramic magnet 42/-; 15 
ohm, 45/-. P. 4 P. Oin., 2/-; 6i and Sin.. 2/6: 10 and 
12 in, 3/6 per speaker. 





BARGAIN PRICE 

£4.19.6*4* 

SUPER DE LUXE version of above incorporating 
ECL86 valve separate bass and treble controls 
and full negative ic-.'.lback. 8 gns.. P. St P. 6/6. 

QUALITY RECORD PLAYER AMPLIFIER 
A top-quality record player amplifier. Size "in. w. x 
2Jin. d. x 5Jin. h. This amplifier (was used In a 
29 gn. record player) emplovs heavy duty double- 
wound mains transformer, ECC83. EL84 EZSO valves 
Separate bass, treble and volume controls. Comp- 
lete with output transformer matched for 3 ohm 
speaker. Readv built and tested. 

PRICE 69'6 P. & P. 4'9. 
ALSO AVAILABLE Mounted on board with output 
transformer and 6ln. speaker ready to fit Into 
cabinet below. PRICE 88/6. P. & P. 6/9. 



QUALITY PORTABLE R PLAYER CABINET 
Uncut motT board. Will take above amplifier and 
B.S.R. or GARRARD Antochanger or single Record 
Player Unit. Size IS x 14 x 8jin. 

PRICE £3.9.6. Carr. 7'6 



HIGH GAIN 4-TRANSISTOR 
PRINTED CIRCUIT 
AMPLIFIER KIT 




TYPE HSL 'FOUR' 
AMPLIFIER KIT 
3 VALVE 4 WATT 
USING ECC88 
ELS4. EZ80 
VALVES 

lor AC mains 200/ 
240v. 

Special features in- 
cluded : 

• Heavy duty double-wound mains transformer 
with electrostatic screen. • Separate Bass, Treble 
and Volume controls, giving fully variable boost 
and cut with minimum insertion loss. • Heavy 
negative feedback loop over 2 stages ensures high 
output at excellent quality w:th very low distor- 
tion factor. • Suitable for use with guitar, micro- 
phone or record player. • Provision for remote 
mounting of controls or direct on chassis. • All 
this builds on to a chassis size only 7ijn. wide x 4ln. 
deep. Overall height 4 t in. • All components and 
valves aro brand new. • Very clear and concise 
instructions enable even the Inexperienced ama- 
teur construct with 100% success. • Supplied 
complete with valves, output transformer (3 ohms 
only), screened lead, wire, nuts, bolts, solder etc 
(No extras to buy). YQ /ft p - * p - 

PRICE i»/0 6/- 
Comprehenslve circuit diagram, practical layout 
and parts list 2/S. (Free with Kits). 
JVKi ** although similar in appearance '.o BASi 
employ! entirely different and advanced circuitry. 



• Peak output In excess of 11 watts. • All standard 
British components. • Built on printed circuit 
panel size 6 x 3in. • Generous size Driver and Out- 
put Transformers. • Output transformer tapped 
for 3 and 15 ohm speakers. • Transistors (GET114) 
or 31 Mullard OC81D and matched pair of OCS1 o,ps 

• 9 volt operation. • Everything supplied, wire 
battery, clips, solder, etc. • Comprehensive easy 
to follow instructions and circuit diagram, 1/6. 
(Free with Kit). All parts sold separately. 
SPECIAL PRICE 45/- P. & P. 3'-. 

Also ready built and tested 62/6. P. A P. 3/-. 
A pai r of TA l'« arc ideal for stereo. 

10/14 WATT HI-FI AMPLIFIER KIT 




£iuie uuiu. - - - . 

Separate Inputs for mike and gram, allow records 
and announcements to follow each other, fully 
shrouded section wound output transformer to 
match 3-15 n speaker and independent volume 
controls and separate bass and treble controls are 
provided, giving good lift and cut. Valve line-up 
2 EL84'a ECC88 EF86 and EZSO rectifier. Simple 
instruction booklet 1/6. (Free with parts). 
All parts sold separately. £6.19.6 %?/" 

Also available ready built and tested complete with 
standard input sockets. £8.15.0. P. A P- 8/6. 
Carrying case for above 28/8. P. * P. 7/6- 



HARVERSON SURPLUS CO. LTD. 

170 HIGH ST., MERTON, S.W.19 CHErrywood 398S 

Open all day Saturday Early closing Wed. I p.m. 

A few minutes from South Wimbledon Tube Station „ v nm ( p '^ s ? ff£n&U 
PLEASE NOTE: P. & P. CHARGES QUOTED APPLY TO UJL ONLY. P. & P. OVERSEAS 

° R &?$ ^Sf&S^SWaW* mVElOPB W1TB ALL sy-jUIRIXS 



SEE 

RIGHT 

HAND 

PAGE 

FOR 

MORE 

ITEMS 



April, 1966 



PRACTICAL WIRELESS 



1099 



LATEST MODEL B.S.R. TU/12 
4-SPEED PLAYER 
AND PICK-UP 

OXLY 69/6£T 

71c metal turn- 
table. Low Hotter 
performance. 200/ 
960 v. shaded 
pole motor with 
90 v. tap for 
valve heaters. 
High gain crystal 



ck-up 



It a 



turnover LP/7 

head complete with sapphire stylii. 





HARVERSONS F.M. TUNER Mk. I 



• Qaar- 

■■. i, t e e .' 
non-driit 

• Per- 
meabili- 
ty tuniiuc 

• Kre- 
queucv coverage 
--- Iimi -Me/s. 

• Balance.! diode output. • Two I.P. stages and 
'liHTitninatnr. # Attractive maroon anil aold 
dial (7 X :«n. flam), • .-<eli-powcred using a good 
'inalllv uiaim transformer and valve n-cllflei. 

• Salves used: EC06S. two RFSO's and EZ80 
(rectifier). • Pull) drilled chassis. • Mr.,- or com- 
pleted tuner 8i8s Of In. • Ah parte wild separat- 
ely. Set of parte It purchased at one time £5.19.6. 
plus 6/6 P. & P. and In*. Circuit diagram and in- 
structions 1/8 pout free. Mark II Version as above 
but complete with manic eye, front panel and 
brackets. *6.1B.6. P. « P. 8/6. 

Mark in Version as Mark I but with output stage. 
(ECL82) and tone control 1T7.7.0. P. * P. 8/6. 

SPECIAL PURCHASE! TURRET TUNERS 

By famou- maker. Brand new and unused. Com- 
plete with PCC84 and PCPSO valves S4-38 Mc ■ IP. 
Biscuits for Channel 1 to A and 8 and 9. Circuit 
diagram supplied. ONLY 8S/- '»rh. P. <s P. :iffl. 
i .^— — 
GdRLER F.M. TUNER HEAD 
**ioo Mc« io.; ilea i. p.. u/.. plus vi- p. & p. 

i KCl>.-, vale... 8/6 -s'.ra,. 

• TRANSISTOR AND DIODE 
SUPERHET 

A flrst-cla&s 2 waveband transistor superhet. 

• Printed circuit panel (slue IS x ZJIn.). • 3 pre- 
aligned 1 F transformers. • HIgh-gtilu Ferrlte Red 
Aerial. • All First-grade transistors. Car aerial 
winding. • Push-pull output. • All ports sup- 
plied with simple Instruction*. All parU wit) 
separately. 8el ol parts i( putcliased at one lime 
OXLV J4.5.0. P. * P. 2/fl (Circuit diagram a/-. 
Free with set of parts.) 

35 OHM SPEAKERS 
SuttaN* S<" »t tei'l/i abort. 2in. Goodmans Ideal 
replacement for most pocket portables. 8/8; 
3jm. 12/6; 7 x 4in-. M/-i P. A P. 2/- per speaker. 

Portable CABINET 

Size approx. 9} x 6J x Siln. Suitable for above 
using 3}in- speaker. 26/-. P. .« P. •>;«, 

COIL AND TRANSFORMER SET 
FOR TRANSISTOR SUPERHET 

3 IF transformers one oscillator coll one driver 
transformer and wound Ferrlte aerial fined, long 
and car aerial coupling). 32/6 complete post '-'.-. 
Q transistor printed circuit board to match 8/6. 
Post 1/-. Circuit diagram 1/6 extra. 

QUALITY PORTABLE 
TAPE RECORDER CASE 

Brand new and unused. Brautiuillv made and 
.:»pe!i-ively Unshed In durk grcj hoary grade 
rexlne. Satin chrome metal grille front and 
chrome fittings. Speacer ancrture » x 4in. Overall 
tfcti 10} w. x 18 d. x 7(ln. h. Will lake any standard 
tape deck or single record player. Limited number 
oulv. Worth at least «S. OUP. PRICE 49/8. 
!•. i P. 5,'.. 

TAPE DECKS 

B.S.B. MONARDECK. Single speed. .'J.'in. per sec., 
simple control uses 5Jin. spool*. £6.15.0. plus 7/il 
carr. and in 9 . 

LATEST COLLARO MAGNAVOX 
'363' TAPE DECK DE LUXE 

Three speeds. 2 track, take* up to 71n. .-pools. 
10- nu. Plus 7'G carr. and In**. (Tapes extra on 
bow.) 



4 Harverson Surplus Co. Ltd. 



NEW VALVES! 

Guaranteed Set Tested 
24 HOUR SERVICE 

1R5. 1S5. 1T4. 3S4. 3V4. DAF91. DF91. DK91. 
DL92, DL94. SET OF 4. 14/-. 

DAF96, DF96, DKS6. DL96. SET OF 4. 23/6. 

1R3 4/- EBC41 6/3 PCL84 7/6 

IS5 3/3 EBF80 5/9 PL36 8/6 

1T4 1/9 EBF89 6/9 PL81 6/6 

3S4 4/3 ECC81 3/3 PL82 57- 

3V4 5/- ECC82 4/6 PL83 5/11 

6K7G 1/3 ECC83 4/6 PL84 6'- 

6K8G 3/3 ECCBo 5/3 PY32 8/6 

6Q7G 5/6 ECF82 6/9 PY33 8/6 

6V6G 3/- ECH35 5/9 PY80 4/9 

10C2 11/- ECH42 7/9 PY81 5/- 

20Iil 11/- ECH81 5/6 PY82 4/9 

20P3 10/6 ECL80 6/11 PY83 5/3 

20P4 13/- ECL82 6/6 PY800 5/11 

20P5 11/6 ECL88 8.'- U25 8/- 

30FL1 9/3 EF39 3/6 U26 8/6 

30LO5 9/9 EF41 5/9 U191 9/6 

30PL13 10/3 EF30 4/3 V301 10/6 

CL33 8/6 EF85 4/6 U301 14/9 
DAC32 6/9 EF88 6/6 UABC80 5/- 

DAF91 3/3 EF89 4/3 UAP42 6/11 

DAF96 5/11 EF91 2/9 UBC41 6/- 

DF33 7/6 EL33 6/3 UBF80 6/6 

DF91 1/9 EL4.1 7/- UBF89 5/9 

DF96 5/11 EL84 4/6 UCC84 7/11 

DK32 7/- EY51 6/11 UCC85 6/- 

DK91 4/- EY86 5/6 UCF80 8/3 

DK92 7/9 EZ40 5/6 UCH42 7/- 

DK96 6/3 EZ80 3/9 UCH81 6/- 

DL33 6/6 F.7.81 4/3 UCL82 7/- 

DL3S 4/9 KT81 6/3 UCL83 9/- 

DL32 4/3 PCC84 5/6 UF41 6/6 

DLS4 5/- PCC89 9/9 UF89 6/6 

DL96 5/11 PCF80 f/3 UL41 7/9 

DY86 6/3 PCF82 5/9 UL84 5/9 

DY87 6/9 PCF805 8/- UY41 3/11 

EABC80 5/6 PCL82 6/3 UY85 4/9 

EB91 1/9 PCL83 8/6 Z77 2/9 
Postage on 1 valve 9d. extra. On 2 valves or 

more, postage 6d. per valve extra. Any 
parcel insured against damage in transit 
6d. extra. 
Office address, no callers. 

GERALD BERNARD 

83 OSBALDESTON ROAD 

STOKE NEWINGTON 

LONDON N.I6 



2 METRES 4 



The thrills ol VHF Amateur Radio! 
Complete Kit. 70-150 Mo/a. costs only 
42/6 (by post. UK, 3/3 extra) also now 
available, new transistor Shorc-Wave 
kit model TR2 10—180 metres, ideal for 
beginners to Ham radio via simplified 
"Easy-Bu'ld" step-by-step Instructions 
from 79/6. Write today enclosing a 
stamped addressed envelope for litera- 
ture and full details. Overseas en- 
thusiasts note we despatch to all parts 
of the world— locai stamp OK for liter- 
ature. "GLOBE-KING" (Rotrd) precision 
standard products tried and trusted by 
Amateurs everywhere. 

JOHNSONS (Radio) 

St. Martins Gate, Worcester 



Trouble getting . . . 

LUXEMBOURG 
CAROLINE 
LONDON ■ 

They're all yours for only 
39/6 with the 

FABULOUS DEWTRON WAVE TRAP 

Just place NEAR your Transistor port- 
able and BOOST all distant stations! 
Extend battery life! NO CONNEC- 
TIONS! Use in car INSTEAD of aerial. 
Send £2 (pott free) 
Money-back guarantee (7 days) 
D.E.W. LTD., Dept. P.W. Ringwood 
Road, Ferndown, Dorset 



ANYONE CAN AFFORD 

THESE NEW JOB TRAINING 

COURSES 

NEW. No. 500 RADIO AND 
TELEVISION COURSE 75/- 

Here at last is your opportunity to own a most com- 
plete course at a very modest null This expanded 
course which now include* television as well as radio 
repair training could get you started on a whole 

The Radio Section of the course was ORIGINALLY 

DEVELOPED BY THE RADIO TECHNICAL 

INSTITUTE, while the Television Servicing Course 

has formed the basis of Instruction provided by one 

of the world's largest television and electronics 

Annul 

Compares lesson by lesson with some courses costing 

ten times as much! You save because you receive 

all the lessons at one time and are not required to 

purchase equipment you may not need. 

The lessons are crystal elear. practical, easy to master 

and use. Early lessons make fundamentals clear even 

to the beginner, while other lessons will give yon the 

practical know-how ol an expert: 

The new S00 Radio St Television Coarse consists ol 

8SS large quarto sin pages ol Instruction, hundreds 

o! illustrations. We positively guarantee that yon 

will be delighted or your money refunded: 

NEW. No. 600 RADIO-TELEVISION 
ELECTRONICS COURSE 85/- 

This Is really big value In home training. Similar In 
details to the above course excepting that vou get an 
extra Sfi pages of Instruction making a total of 40$ 
quarto alxe pages. Hundreds of Illustrations. Inclu- 
des all the usual subjects plus Radio Transmitter 
Circuits, Electronic Test Equipment, Thvratron 
Tubes, Inter-f'i.uiDiunlr-atius, BOtmd Level Meters, 
Servicing l*rlnled Circuits and many more similar 
items. This course could be your Hist step into the 
fascinating world of electronics! 

No. 400 ELECTRONICS COURSE 45/. 

A complete home*'. ody course of SC lessons. Cousins 
of 2W large quarto site pages of Instruction. Comes 
complete with Instructor's ootsrs and test questions. 
This is a modern course that leaches wBbotd r -- a 
ing to comic strip methods . . . Thousands of readers 
of this magazine have taken this course and -ij..- I 
every minute of It... Why not you? Clip i til* 
coupon for your free trial offer now! 

No. 19. REFRIGERATION SERVICE 
MANUAL 27/6 

Learn refrigeration! This manual Is packed solid with 
information to enable you to start in refrigeration 
right away I Used by many leading firms as u stand- 
ard reference. Features :)tl4 pages, 157 Illustrations. 
bound In cloth. An excellent book DOW offered d.i i be 
Qrst time! 

UNCONDITIONALLY GUARANTEED TO 
GIVE COMPLETE SATISFACTION 

Any course not satisfactory may be returned within 
10 days post-paid for full refund or credit of the pur- 
chase price. 

IF YOU SEND CASH WITH ORDER WE WILL 
INCLUDE A FREE BOOK worth 4/6 to 5 - if 
bought separately. By scuding cash you reduce 
book-keeping and other coats which we pass back to 
you. But you must Include cash at the time ol order 
to get this special offer! 

* * * * FREE TRIAL OFFER • * * * 
PAY ONLY 5/- per week if you wish. 

To: SIM-TECH TECHNICAL BOOKS DEPT. G.5. 
Gater's Hill, Welt End. Southampton. Hants. 



□ 



Pta 



send the courses I have circled. 
No. 400 No. 19 



NO. 000 No. 000 

If not delighted 1 may return any book post-paid 
without further obligation on tuv part. Other* i-.- 1 
will pay cash price or 0/- weekly (10/- fortnightlo 
commencing not later than 10 days after dcliverv. 
I am over ai years of age. (If under'ai parents should 
place order). 

I enclose cash to the sum of t 
1 understand you will refund this 
money If i am not 100°„ satis- 
fled and I return the book with- 
in 10 day.. 

Please send me tbe Iree hooktsj I km ti.-k - .1. 
Oscilloscope Rook K!e.'tr.mic OsbdfpMs Book 
Translator Book Radio Instrument Boo* 



1100 



TEST METERS 




20,000 O -P.V. MODEL TP 68. Beads voltage up to 
1,000 D.C. at 20,000 ohms per volt and A.C at 
lil 000 O.P.V.j D.C. Current to 600mA; Resistance 
to' 10 Han.! Capacitance to O.luJP; Decibels from 
—•20 to +38. Size 3jln. x Sjln. x l«ln., 25.19.6. 



2,000 OJP.V. MODEL TP 10. Reads A.C. and D. 
Volts up to 1,000 D.C. Current to 600mA; 
Resistance to 1 Meg.; Capacitance to luJs 
Decibels from —20 to +36; Output Jack for 
Audio Measurements. Blae Si X 6 X l.ln. 
«3.19.6. ^^___^__ 



S'J.OOQ OHMS PER VOLT MODEL 600. Reads 
voltages up to 1,000 D.C. at 30,000 ohms per volt 
and A.O. at 16.000 O.P.V.; D.C. current to 12 
amps. Resistance to 60 Megs.; Decibels from —20 
to +66; Incorporates Internal buzzer for audible 
warning of direct aborts and blocking condenser 
for A.F. output measurements. Size S 5 /„x« In 
xSzin., 28.19.6. 



20 000 OHMS PES TOLTTESTMETEB MODEL 
700. Beads A.C. and D.C voltages up to 6.000. 
Alternating and Direct Current up to 10 amps. 
Resistance up to 50 Megohms, Dcolbels from —10 
to +42dB. Internal buzzer for audible warning 
of short drcuita or continuity and fitted with 
automatic overload protection for movement. 
Meter size «ln. X 2jin., overall dimension 7Jln. X 
6jln.x3}in. Has rigid handle which can .be 
swivelled for use as a tilt support. ONLY S17.10.0. 



TRANSISTORISED TEST EQUIPMENT. Full? 
guaranteed, brand new. By NOMBBEX: 150 
K.o/3.— 350 Mc/s. Signal Generator, 49.10.0. 
Resistance-Capacitance Bridge, 68.6.0. 1-16 volts 
DC. Power Bupplv. 16.10.0. Audio Generator 
10100.000 e»s, C6J6.0. Inductance Bridge, 
S18.0.0. . 



VALVE VOLTMETEE. D.C. Input Impedance 
1 1 Megohms. 7 Voltage ranges, D.C. to 1,800 A.C. 
[,. 1,500 R.M.8., 4,200 Peak to Peak. Bestotance 
a ohm to 1.000 Megohms. Centre zero setting for 
receiver alignment. Complete with A.C. /D.C 
probe and leads. Full illustrated details on 
rquest. ONLY £13.19.6 (Post 3/6). 



FREQUENCY METERS TYPE LM. Frequenc: 
range 126-20.000 kefs, in 2 bands. This Is th 
Lnited States Navy Model of the well-known 
BC221 Frequency Meter, but has many additional 
features which increase its usefulness. Voltage 
•labilisation circuits and Crystal control ensure 
extreme accuracy and in addition It is fitted with 
an Internal Modulation switch to allow use as a 
Signal Generator. Size only 8!in. X 8in. X 8iin. 
ONLY 415. 



PRACTICAL WIRELESS 




HI-FI CONTINENTAL 
STEREOPHONIC RADIOGRAM CHASSIS 




Magnificent 'Continental' Stereophonic 
Radiogram Chassis with piano key switches, 
built-in ferrite rod aerial. Complete with 
two 10" elliptical loudspeakers, plus a mono/ 
stereo 4-speed autochanger. Complete 
£29.19.6. Chassis only 19* gns. 
Special terms available of £4.10.0 
deposit followed by 18 monthly pay- 
ments of £1.13.0 (total H.P. of £34.4.0) + 
15'- P. & P. Send £5.5.0 now. 



IMPERIAL HI-FI 
STEREOPHONIC RADIOGRAM CHASSIS 



•&**%&#%» 




The Imperial Stereophonic 4 waveband 
chassis has the most advanced specifications 
yet offered in this country. There is a built- 
in ferrite rod aerial, seven piano key buttons. 
Long-Medium-Short and VHF bands. Com- 
plete with two 10* loudspeakers plus a 
mono-stereo 4 speed automatic record 
changer. Complete 39J gns. 

Chassis only 29* gns. 

Special terms available of £6.4.6 deposit 
followed by 24 monthly payments of 
£1.15.10 (total H.P. £44.4.6) + l7'6P.&P- 
Send £7.2.0 now. 



HI-FI EMPRESS RADIOGRAM CHASSIS 



VARIABLE VOLTAGE TRANSFORMERS. „ Fully 
shrouded. Input 230 v. A.C, 50/60 cycles. Output 
0-260 v. 2.6 amps, type £5.17.6. 5 amps, type 89. 
10 amps, type £18.10.0. 20 amps, type £82.10.0. 



STANDARD TRANSFORMERS 

Vacuum impregnated, Interleayed E.8. screen 
Universal mounting. Size 4in.x3iin.x2Jm. 
ALL BRAND NEW 18/6 each. Post 2/8. 
Type 1. 260-0-250 v. 80 mi., 6.3 v. 3 a, tapped at 
4 v. 4 a, 6.3 t. 1 a. tapped at 4 v. and Sv. 2 a. 
Type 2. As above but 350-0-350 v. 80mA. 
Type 8. 80 v. 2 a. tapped at 12, 15, 20, and 24v 
to give 3-4-5-8-8-9-10 v.. etc. ^^^^ 




April, 1966 

SWLs • SWLs ■ SWLs ■ SWLs 

Hark! 

Hark! 

-the DX is calling! 



HARRIS ELECTRONICS 

(London) LTD. 

138 GRAY'S INN ROAD 

LONDON, W.C.I. 

Telephone: TEBmmxu 7937 
Please include carriage eoil on ALL Uemt. 
Trading noon 9 a.m. — 6 p.m., Monday— Friday. 
Closed Saturday. We are 2 mini, bom High. Hol- 
born (Chancery Lane Station) and fi mini. W bos 
lrom King's Cross. ^^^^^^^^^^^^ 



This fabulous 'Empress' Hi-Fi radiogram 
chassis is offered complete with 10 loud- 
speaker plus 4 speed autochanger. At 
only 23 gns. this is the bargain of the year. 
Chassis only IS* gns. ...,_,. 
Special terms available of £3. 12.6 deposit 
followed by 18 monthly payments of 
£1.6.7 (total H.P. £27.1 1.0) + 15/- P. & P. 
Send £4.7.6 now. 

All Lewis Radio equipment including valves are roily 
guaranteed for one year. Send your cheque or P.O. 
today while stoeta l ast to Dept. P.46. 



LEWIS 



radio 



LEvfys RADIOi'lOO.CHASE SIDE, SOUTHGATE 
LONDON. N.14. Telephone: PAL 3733/9666 




Special RX tuner 
4§- x 3,' x 3," 



JOYSTICK 



Variable Frequency 
ANTENNA SYSTEM 

This revolutionary and pat. pend aerial 
system possesses the unique property o( an 
even response over all frequencies between 
1.4-30 Mc/s. , „ I 

Every JOYSTICK Aerial System is supplied 
complete with feeder and an aerial matching 
unit. Just connect your RX— it Is ready to go 
and gives an unprecedented lift' to signal 
airenzths especially for 'clln" and "cave" 
dwellers— EYES FROM UNDERGROUND! 
Naturally the advantages of using the 
'JOYSTICK' "up-in-the-clear" are even 
greater! ... 

4.000 Joystick aerials all over the world have 
alreadv shown that this is the first major 
break-through for 20 years in the field of 
ai-rial*. The performance for such a compact 
nnit <7'6" assembled) is staggering. Even the 
sceptics have been convinced once they have 
understood the basic principles and have 
followed the simple tune-up' procedure 
given in the detailed instructions. 

New Joystick Range 

There Is now a whole new range of Joystick 
Aerial Systems — made to match your Q 1 a 
your rig and your pocket! The SYSTEMS 
cover SWL, TX/RX, indoor and outdoor 
mobile and even a new JOYMA3T! Mud* 
onlv in the finest materials the SYSTEMS 
are reliable and permanent! Read all about 
them In our new brochure — 
GUARANTEE: Partridge operate a rigid 
100% Money Back Guarantee ii you're no 
completely satisfied! 

Head testimonials from all over the world 
"Four different receivers showed improve! 
performance over a dipole" reporta th 
U.S.A. C.Q. Magazine. 
"Excellent results. Australia, Ceylon. Bout 
Africa at good strength although latel 
reception conditions have been poor. 
VV. Cuinmlngs, Lossiemouth, Scotland. 

RCA D A I I This ticket wul brln 
l»tMI/ ** U, "vouthcnewbrochur. 

ABOUT IT! by returo of P0B 



PARTRIDGE ELECTRONICS LTD. 

Caister House. Prospect Road, 
Broadstairs, Kent. TeL THASET 621536 



April, 1966 



PRACTICAL WIRELESS 



1101 





Also in the April issue 

LEISURE CHAIRS FOR 
LOUNGE OR LOGGIA 

SUN LOUNGE FOR SMALLER HOUSE 

BOW-FRONT WARDROBE 

FLOWER-POT TROUGHS 

BEDSIDE CUPBOARD 

WOODTURNING FOR PLEASURE 
AND PROFIT 



A NEW 'PRACTICAL' FOR 
THE EXPERIENCED AMATEUR 
AND THE BEGINNER 

Packed with fascinating new projects, new ideas 
and new techniques, practical woodworking, 
brings you the guidance you need to tackle 
any kind of woodworking job with the flair and 
finish of a professional. 



FREE! 



16-Page Booklet 

HOW TO MAKE 
WOODWORKING JOINTS 

Covers every type from simple notched and 
tenon to modern glue-laminating techniques. 



FREE! 



Construction Plan for 
SECTIONAL GARDEN WORKSHOP 

Full instructions on construction and erection. 

EXTRA ! Fold-out Sheet to Build 

• JOINER'S TOOL BOX 

• FOLD-AWAY WORK BENCH 



EXTRA! 



Locks and Hinges Data Sheet 



BIG DEMAND! MAKE SURE OF YOUR COPY -26 



, 



1102 



PRACTICAL WIRELESS 



April, 1966 



»»»»*•*• 



D. & B. TELEVISION (WIMBLEDON) LTD. 

131 KINGSTON ROAD • SOUTH WIMBLEDON • LONDON S.W. 19 
Telephone: CHErrywood 3955 



ALL 



BRAND NEW VALVES GUARANTEED 3 MONTHS 

Postage and Packing on Valves 6d. each. 



AZS1 

HAF91 

1JAF96 

DF91 

DF92 

l)l"9rt 

UK91 

DK92 

UK9S 

1)1.93 

DL94 

DL96 

DYS6 

DY87 

EABCSO 

EAF42 

EB91 

EBC33 

EBC41 

EBG81 

EBFSO 
EBFSO 
ECCS1 
BQCS9 
ECC83 

i-.i ca i 

ECC35 

ECF80 
ECH35 
ECH42 
ECHS'l 
ECL80 
ECL82 
ECL33 
EOLSfl 



10/8 


EF80 


7/10 


EFS5 


7/10 


EF86 


6/8 


EF89 


6/8 


EF91 


7/10 


BBSS 


7/10 


EF183 


7/10 


EL33 


7/10 


EI.34 


6/8 


EL36 


6/8 


HU: 




EL84 




EMsO 


71- 


EM81 




EM84 


8/6 


BM85 


4/8 


EV51 


11/8 


EY8G 




BZ40 


6/6 


KZ41 




V./.Vl 




EZU 


7/4 


EZ90 




GZS2 




GZ34 


7/8 


HBCS0 


7/4 


PABC8< 








PCC88 




PC97 




PCC84 


7/4 


PCC85 


8/8 


PCC83 


10/6 


PCC89 


8/8 


PCC189 


open 9 a 


m. to 6 p. 



71- 
71- 
9/4 
7/- 
11/- 
8/- 
9/8 
10/6 
9/9 
9/9 
8/- 
6/4 
7/8 
7/8 
8/8 
10/- 
71- 
71- 
5/6 
5/6 
5/6 
5/6 
5/- 
11/- 
11/- 
6/4 
7/6 
8/10 
8/10 
7/6 
7/4 
7/4 
12/6 
10/6 
10/8 



PCFS0 

PCF82 

PCF86 

PCF801 

PCFS02 

PCF806 

PCLS'2 

PCLS3 

PCLS4 

PCL85 

PCL86 

PE36 

PL81 

PL82 

PL83 

PL84 

PL500 

PY33 

PT80 

PY/81 

PY82 

PY83 

rem 

PY800 

PY801 

UABCS0 

UBOU 

UBC81 

CBF80 

UBF89 

UCC84 

UCC85 

TJCFSO 

DCH42 



8/4 

9/4 

10/6 

10/- 

10/- 

10/- 

8/4 

9/8 

8/8 

8/8 

8/8 

10/- 

8/4 

6/4 

8/4 

71- 

14/- 

9/6 

6/- 

7/- 

5/6 

9/6 

7/- 

'/- 

i 

V- 
It- 

8/10 
7/4 
9/4 
9/6 



OCH81 

TJCL8'-' 

UCL83 

UF41 

UF42 

BF80 

UFS5 

UF89 

TJL41 

DL46 

UL84 

TJY41 

UY85 

5Y3 

6Z4 

6V6 

6X5 

K19 

U25 

U28 

TJ191 

U193 

TJ361 

U281 

U282 

U301 

U801 

UU9 

6F1 

6F13 

6F14 

6F15 

6F23 

6F24 



7/3 
8/8 
10/8 
7/6 
9/- 
7/6 
7/6 
7/- 
7/6 
10/6 
8/8 
5/6 
5/6 
5/5 
7/6 
7/7 
7/5 
14/8 
10/3 
10/6 
9/9 
71- 
U/8 
13/9 
13/9 
13/9 
19/- 
8/6 
9/6 
12/8 
16/- 
12/6 
10/8 
10/9 



to 6 p.m. Monday. Tuesday, Thursday and Saturday; 9 a.m. toy7 p.m. Friday. Closed 



6F25 


10/9 


6328 




6L1 








6/30L2 












10F9 


8/- 


10F18 




10P13 




10P14 






11/- 






20P1 


15/- 


20P3 


12/- 


20P4 


13/- 






80(36 


9/6 


30C17 




30C18 




30F5 




30FL1 




S0L16 




30L17 


11/6 


30P12 


9/6 


30P4 


12/- 


30P19 


12/- 


80PL1 


12/8 


S0PL13 


12/6 


30PL14 




30FX12 


10/6 


30FL14 




30FL18 


10/6 


all day Wednesday 





We are open a a.m. to o p.m. nonuay. i««»), * U u.~=, ,, _-"—-'-' ....._._ — . — .. n a r» .4 J 

SERVICE SHEETS TELEVISION ! ! ALL MAKES AND MODELS 4/- P. & P. 4d 



*~~ 



.»«>»» **»»**^^*~ 



.^.^^^^^ >»^.^»^^^ 



FAMOUS FOB THIRTY YEARS for 
SHORT-WAVE EQUIPMENT Ol QUALITY 



H.A.C. 



SHORT-WAVE 
KITS 







H.A.C. were the original suppliers of abort- 
Wave Receiver Kite for the amateur con- 
structor. Over 10.000 satisfied customers— 
Including Technical Colleges, Hospitals, 
Public Schools, B.AJ., Army, Hams, etc. 

IMPROVED 1968 RANGE 
1-Valte model "OX", oomplete kit. Price 34/6 
Customer) say: "Definitely the best one- 
valve S.W. tit available at any price'. This 
tit contains all genuine Short-Wave com- 
ponents, a drilled chassis, accessories and lull 
instructions. Ready to assemble and or" 
course, as all our products, fully guaranteed. 
FULL RANGE of other kits still available 
including the famous model 'K'. prico 77/-. 
Before ordering call and Inspect a demon- 
stration receiver or send for a descriptive 
catalogue and order form to: — 

"H.AA" 8HORT-WAVE PRODUCTS 
(Dent. P.W.), 44 Old Bond St, London W.l 



WORLD RADIO & TV 
HANDBOOK 1966, 28/- 

by JOHANSEN. postage 1/3. 
ABC's of Electronic Organs by Crow- 
hurst. 16/-. P. & P- 1/-- „ _. . .. 
Electric Guitar Amplifier Handbook by 

Darr 24/-. P. & P. !/■• 

Transistor Circuit Manual by Lytel. 35/-. 

Transistor Electronic Organs for the 
Home Constructor by Douglas. 18/-. 

Transistor Substitution Handbook, new 

ed. 12/6. P- & P. 1/-- . _ 

101 Wavs to use your Signal Generator 

by Middleton. 18/-. P. &P.1/-. 

Practical Transistor Servicing, new ed. 

by Caldwell. 24/-. P. &P. 1';. 

Where possible 24 hours service guaranteed 

UNIVERSAL BOOK CO. 

12 LITTLE NEWPORT STREET, 
LONDON, W.C.2 

(adjoining Ldsle Street) 



DIGITAL COMPUTER 
A simple digital Adder/Subtractor using switch- 
es and lamps only. A fascinating demonstration 
of Binary arithmetic. Full circuit, wiring dia- 
gram and notes on the Binary system, 3/8. 
NOUGHTS AND CROSSES MACHINE Uses 
standard miniature switches and lamps only. 
Thi3 machine cannot be beaten. Full circuit, 
wiring diagram and Instructions, 3/6. 
1% High Stability Resistors 
J watt 1%. 2/- each. Full range 10 ohms to 10 
Meg. Many special voiue3 ror meter multipliers 
etc. in stock. 

1% Wirewound Resistors 
1%, 1 watt, 1 onm to oK, 3/- to 20K, 4/3; i% 
add 3d. Your value wound to order. Shunts 
down to 0.1 ohm. 

High Resistance Phones, 10/-, post 1/-. 
100 Resistors, 1, 9 and 5% assorted, 9/8. 
Signal Injector Kit, 10/-. po3t II-. 

PLANET INSTRUMENT CO. 

25 (W> DOMIHION AVEHUE, LEEDS 



BBC2 (625 LINE) TV AERIALS 




Mast Mounting Arrays, ? element 45/-- 
wide spaced high gain. 11 element 55/-: 14: 
element 62/6. Wall Mounting with 
franked Arm 9 element 60/-:wide spaced. 
high gain. 11 element 67/6; 14 element 
75/-. Chimney Arrays Complete. 9 ele- 
ment 72/-; wide spaced high gain. 11 ele- 
ment 80/-: 11 element 87/6. Loft Arrays. 
7 element 32/6: wide spaced high gain, 11 
element, with Tilting Arm. 62/6; 14 ele- 
ment 70/-. All high gain units have 
special Multi-rod Reltector. Low loss 
co-axial cable 1/6 per yard. L'HF tran- 
sistor pre-amps from 75/-. 



BBC 



ITV • F.M. AERIALS 

BBC (Band 1). Tele- 
scopic loft 21/-. External 
S/D 30/-. 

ITV (Band 3). 3 Ele- 
ment loft array 25/-. 5 
element35/-. Wall mount- 
ing. 3 element 35/-. 5 
element 45/-. _ _ 

Combined BBC/ itv Loft 
1+3, 41/3; 1+ B *8' 9: 
Wall mounting 1 +3 56/3; 
1+5, 63/9; Chimney 1+3. 
63/9: 1 + 5 71/3. 
VHP transistor pre-amps 
from 75/-. .__, „, 

F.M. (Band 2). Loft S/D 12/6. "H". 30/- 
3 element. 52/6. External units available. 
Co-ax cable 8«i- yd- Co-ax plugs. 1/3. 
Outlet boxes 4/6. Diplexer Crossover 
Boxes. 12/6. C.W'.O. or C.O.D. P. & P. 4/6. 
Send 6d. stamps for Illustrated lists. 

K.V.A. ELECTRONICS (DeptfW.) 

27 Central Parade, New Addington 

Surrey 

LOD 2266 




April, 1966 

Your complete basic guide 
devoid of mathematics 
and circuitry 

BEGINNER'S 

GUIDE TO 

COLOUR 

TELEVISION 

by Terence L. Squires, 
A.M.Brit.l.R.E. 




Explains fully how the signals 
are created in the television 
studios, how they are trans- 
mitted and the techniques 
used to receive and display 
them. Covers: Historical Out- 
line - The Colour Signal - The 
Chrominance Signal - Colour 
Transmission - Receiving the 
Colour Signal - Domestic 
Aerial Systems - The Receiver 
Block Diagram - The SECAM 
Receiver etc. 

128 pages, 58 diagrams 

only 15s. net 

from all booksellers 

... or, in cose of difficulty, 16s 3d by post 
from George Newncs Ltd.. Tower House, 
Southampton Street, London W.C.2. 

N E W N ES 



C 



PRACTICAL WIRELESS 
PADGETTS RADIO STORE 

OLD TOWN HALL,. 
LIVERSEDGE, YORKS. 

Telephone: Cleekheaton 2866 

18 Set Receiver. 4 Valve Battery S/H 6-9 

mo/s. Clean condition 18/6. Post. 6/-. 

68 Set Receiver. 4 Valve Short Wave 

Battery Set. New 16/6. P/P 6/-. 

MM) Micro-Amu Meter from 18 Set Tx. 

7/6. P/P 1/9. 

New MM) Micro-Amp Meter from 68 Set Tx. 

18/6. P/P 1/9. 

Muirhead Pattern Slow Motion Drives. 

Removed from units 5/-. P/P 1/9. 

Magic Eye with Holder. Ex Units Octal 

Ba?e 8/6. P/P 1/3. 

Now Boxed Tulip I nit, CR103. Complete 

with Two small CRT Tubes VCRX3&3 and 

VCRX2S8. Plus SI small valves and O-lma. 

meter. Relays removed. 57/-. Carr. 10/-. 

Reclaimed Tubes. Six months' guarantee. 

AW43/80. 30/-. MW43/S0. 30/-. MW43/6P. 30/-. 

CRM172. 30'-. CRM142. 17/-. 12' Tubes 10/-. 

17" tubes perfect but without guarantee, 

17/- each. Carriage on any tube in G.B. 10/-. 

Specially Selected Nearly New Valves 

with 6 months' guarantee. Single valves 

Post. 7d 

B07 

ARP12 

BCLW 

eccs:i 

ECCe2 



1103 



PY33 

PCC84 

PCF80 

PL36 

PL81 



6/- 
5/6 
5/6 
6/- 
5/6 



F.F91 
6K7 
6K8 
6V6 



r.;- 

l'G 
.'CO 
5- 
4/3 

VALVE LIST 

Fx Equipment, 1 month-' guarantee. 
Single Valves Post 7d. 
KT36 
PCF80 

PCC84 
PCr, 82 
PCI, 83 
PCL84 

PCL85 
PZ30 



EF8C 


1/6 ] 


ECL8Q 


1/6 1 


BF91 




EB91 


8d. ' 


EBF80 




F.CC81 




BCC82 


3/- | 


ECC83 


4/- 1 


EL84 


5/- 


EY51 


8/6 ' 


EF50 


1/- 


EYB6 




6K25 




6U4 


5/- ! 


6P25 


5/- ■ 



PY81 

PY82 

PL81 

PL38 

PY33 

6B8 

6F1 



5/- 
8/- 
2/- 
«• 
3/- 
3/- 
3/- 
5/- 
1/6 
1/6 
4/- 
5/- 
5/- 
1/6 
!/• 



6F14 

10C2 

30P13 

10P14 

20D1 

20L1 

20P1 

20 P4 

0801 

U329 

U301 

u:9i 

U281 
IJ282 
U25 



Motors removed from Washing Mnohines 

i h.p. with pulley. 26/-. Carriage 10/- 
Hoover MK1. 15/-. Carriage 7/G. ' ,h.o. moto 1 -. 
IS Amp. Douhle Sockets. Brown Surface 
Type. 3/-. Post 1/8. 8 for 18/-. Post Paid. 
New Jap Earpieces complete with lead and 
plug. 8 ohms. 3 or 5mm., 1/11 or 80/- per doz. 
Post Free. 

Diodes. Top grade. No duds 8/- per doz. 
Post Paid. 

Perfect Speakers removed from T.V. sets. 
Round 8". 6/-. Rola 6 x 4. 3/-. Goodmans 
7x4. 5/-. 6" Round. 3/-. Philips 5" Round, 
3/-. Plus Post on any Speaker 2/9. 6x4. 
6" and 5' Round Speakers. 6 for 20/-. Post 
Paid. 



SWIVEL STORAGE RACKS. Ideal for 
Nuts and Bolts, Resistors, etc. Unbreak- 
able Plastic Trays S{" x 3" x li" with Two 
Divisions with Brackets for fixing to wall. 

4 trays •'- 

6 Trays »'- 

8 Trays 12'- 

P. & P. 1/4 any size. 

JIGTOOLS, PENTrRCH, CARDIFF 




EQUIPMENT CABINETS 
OF DISTINCTION 




Imperial 



• Illustrated In this advertisement are 
two fine cabinets from the Lewis 
Radio Range. 

• These Cabinets are Just two of a 
really extensive range. 

• Each one carefully made by British 
Craftsmen and soundly constructed 
from the best materials available. 

• Fill In coupon below to obtain FREE 
catalogue showing this wonderful 
range of cabinet*. 

: : : : : : : : : : : : :;:::vx::::::v:::x;x : :^:;:;:;:;:;X:::y::::::;X:X::: 





Lowflex 



f&£ 



1 

THE NEW LEWIS | 
RADIO CATALOGUE | 

assist your choloe of I 



Designed 

I Cabinet. 
The New Lewis Radio Cabinet Cata- 
Ilogue— the most comprehensive ever 
prepared. Sent absolutely FREE! 
Please tend now FREE cabinet catalogue. 




1104 



PRACTICAL WIRELESS 



April, 1966 



Head Office Md Warehouse 

HA WE5TBOOBHE GBOYE 

LONDON W2 

Tel.: PARK o(Hi 2 :: 

FIciK write for fall catalogue 



Z & I AERO SERVICES LTD. 

Please sead all correspondence and Mail-Orders to the Head Office 

When sending cash with order, please Include 2/8 In £ EOT postage uud handling 

MINTMCM CHARGE 1.'6. Ho C.O.D. orders accepted 



Retail Shop: 

85 TOTTENHAM COURT KOAD 

LONDON Wl 

Tel.: LANgham 8403 

Open all day Saturday 



OA2 6/- 6AHB W/-I6F28 10/8 

OA3 11/- BANS 10/-6I"I2 3/- 

OB2 8/- 8AQ4 5/- 6G6G 8/8 

OBS 8/- 6AQ3 6/- 6116 2/- 

Ot'.l 8/- 6AQSA 7/6 'ill 9/- 

OU:l 6/- flAKS 8/-|iijri 6/6 

IVi 8/. BARB 6/- BJ5GT 4/8 

lASOT.'OW- BAR 8 17/6 1 6.16 3/6 

1A7GT 8/.'6AS» 5/-IBJ7 9/- 

1B3GT 7- «ASU 5/- 6J7g 5/- 

1050X 8/- BA87G 20/- 0K6G 6/- 

1D5 7/6 6AT6 4/8 6K7G 2/- 
1GBOT 7/- 6AL"4GT 9/- 6K7GT 6/- 

1H5GT 7/- ' 6AI-6 6/-i6K« 8/- 

1L4 2/6I6AV0HTU/- 6K8G 4/- 

1L6 17/6I6AV0 8/- BK23 7/6 

1VSGT 8/- 8AVV8A14/-UK2S 24/- 

1R 4 8/- 6AX50T 61.1 10/- 

1R5 6/- 18/6HIL6GA 8/- 

184 6/- 6B7 5/-J6L7 6/- 

185 4/6 6B8 7/-Ul.lS 8/- 
1T4 8/. 6B8G 8/6 '8X7 8/- 
1T0GT 6/- 6B8GI 5/- 6N7GT/G7/- 
1U4 6/-6BAB 6/-! 6P1 11/- 

6/. CBA7 15/- ;0P2fl 



1U5 
IV 



57- 
10/- 
71- 
51- 
30/- 
6/- 
12/- 
2052 18/- 
2C53 50/- 
2CW4 12/- 
2D21 8/- 



6BC4 17/6 8P28 



1V2 

1X2B 

2A8 

2A4G 

2C26A 

2C51 



40/- 
30/- 
12/- 
4/- 
71- 
6/- 
80/- 
5/- 
40/- 
4/- 
60/- 
6/6 



2E24 

BH26 
■; 2021 
■•;"•■ SA 4 
*, 3A6 
•1SB7 

8B22 

3B24 

8B28 

3D6 

3E29 

8Q4 

3QDGT/G6/6 

334 6/- 

3V4 6/- 

4D1 *l- 

4THA 10/- 

5R4GY 8/- 

6U4G 6/- 

S Li 4GB 6/6 

6V4G 8/8 

5Y8GT 5/- 

0X4G 8/- 

5Z4G 8/- 

' 6/30L2 10/6 

6A6 4/- 
6A8 
6AB4 
6AB7 
8AC7 
6AF4 



12/6 

12/6 
67- 

(II- 
81- 
!>/- 

6/- 
8/- 

B- 



6BEB 5/6 6Q7G 
6BGBG 15/- 8 ICV 
6BF6 6/- B8A7 
6BH6 7/6BSC7 
0BJ6 8/- 6807 

6BJ7 7/- 68J7 
6BK4 85/-.68K7 
6BK7A 9/- 6SL7GT 61- 
BBI.7GT 9/- 6S.V7GT 4/6 
6BS6 7/6 6SQ7GT 5/- 

11/- '6887 8/- 
8/- 6T8 71- 

12/- 8U4GT 10/6 
5/-I8C7G 7/- 

17/- BC8 6/6 



6BQ6 
6BQ7 
6BB7 
6BB8 
6B87 
6BW6 

6BW7 10/- 
6BZB 6/- 



9/6 



6BZ7 

6C4 

6CS 

6C5G 

6C6 

6C8G 

6C6 

6031 

6CB6 



11/- 



6U8A - 9/6 

6V6 * 9/- 

6V6G 67- 

, 8V6GT 7/6 

2/e;c,wc5 71- 

61- 6X4 4/- 

5/- BX6G 4/6 

4/- 6.X5GT 6/- 

~ 624 6/- 



71- 
11/- 
8/- 
5/- 



6CD6GA17/- 
6CG7 10/- 
6CH6 6/- 
80L6 9/- 
6CW4 12/- 
6CY5 10/- 



7B5 
7B6 

7 I'. 7 



6CY7 

61)3 

6D6 

-. 6DC6 

8/- 6DK6 



Da 
«/. 

4/- 
10/- 



6AF6G 11/- 

6AG5 2/6 

6AG7 8/- 

6AH6 10/- 

6AJ5 9/- 

6AK5 

6AKB 

6AK7 

6AL5 

6AM6 

6AN4 



6DS1 
BBA8 
6BVS 
6F1 

6F6 

6F6G 

6F7 

6FSG 

-, ,BFH 

8/6 6F13 

7/- 6F14 

6/- 6F10 

3/- BFI7 

4/-!6F23 

15/-i6P2fi 



11/- 
7/6 
3/- 
12/6 
«/- 
15/- 
11/- 
12/- 
14/- 
8/- 
5/- 
5/- 
5/- 
6/- 



7Dfi 
7E5 

7I-:b 



7Y-I 



9BW6 

10C2 
10D1 

I0K1 

10F8 

10 VQ 
10F18 
8/6 I'd.l 
IS/- 1BP13 12/6 
11/- I HP 14 13/- 
6/- 10 Y 16/- 
11/6 11 OS 7/- 
6/e|lll>S 71- 



10/- 
111- 
71- 
10/- 
71- 
6/- 
8/- 
8/- 

i 

14/- 

10/- 
91- 

18/- 
8/- 
6/- 
71- 

13/- 
71- 

14/- 
8/- 

10/- 
9/- 
7/6 



12A6 3/- 
12A7 10/- 
12AG6 8/- 
12AD6 81- 
12AH7GT 

8/- 

12ALS 71- 
12AQ5 7/- 
12AT8 6/- 
12AT7 il- 
12AIJB 6/- 
12AU7 5/6 
12AVB 6/- 
12AV7 8/- 
12AW6 20/- 
12AX7 6/- 
12AY7 10/- 
12B4A 9/- 
12 BAB 8/- 
ISB86 5/6 
12BH7A 71- 
12BY7A10/- 
12C8 4/- 
12E1 20/- 
12F5GT 8/- 
12H6 8/- 
12J5GT 8/- 
12J7GT 7/8 
12K5 10/- 
12K8 8/- 
12Q7GT 5/8 
128A7 71- 
12807 4/- 
12SK5GT9/- 
128G7 4/- 
12S117 4/- 
12SJ7 4/- 
128K7 5/- 
12SQ7GT6/6 
128B7 5/- 
12Y4 8/8 
13D1 6/- 
1SD3 5/- 
1407 10/- 
1437 18/- 
19AQ5 6/- 
19G6 16/- 
20P1 
20P3 
20F4 
20P5 
25A6G 
25 C5 
25Z4G 



. ., _ , EBI.-.ll 11/- ' BM31 5/- PQTJ189 12/- THSS8 8/- 

First Quality Fully Guaranteed t;bi..ii 18/- ' BM34 12/- PGF80 7/6 TH3321 71- 

— I - ■ ' BCS3 10/- I EM35 8/- POF82 8/- TP20 5/- 

^^sl 1 X# PMB 191. P.M71 19.16 Pl-I-'HJ R/- TTlo 35/- 



ELECTRONIC VALVES 



35D6 12/- 
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BBZa io/- 

35Z4G 4/- 

35Z4GT 8/6 

35ZSUT 8/- 

42 5/- 

431D 8/- 

50A5 12/- 

50115 71- 

5001 8/6 

50L6GT 8/6 

50Y6GT10/- 80M 
o/. 6060 
»■ «07> 



>763 



840 
1845 
5847 

S963 

59BS 
6806 
0021 

llilns 



71- 
12/- 
10/- 
10/- 



KC88 

Ef -- 

ECHO 2/6 EM81 

EC9I 5/- EM84 

EC92 6/6 | EMS7 

BRAND K ' , ' xl 5/ " ,;n;u 

' " BOOM 10/- EX91 

ECC70 15/- EN92 

BOOM 4/- EY51 

ECC82 5/6 EY70 

BCOn 6/- BT81 

ECCK4 71- EY83 

BCOB6 6/6 EY84 

ECC8B "/- BS86 

Bl B7 



12/- earn 12/6 pufs! 8/- ttis 36/- 

12/- 1 BH8Q 7/- , POF88 9/- , TT21 35/- 



AZ1 
AZ11 
AZ12 

A/;u 



7BC1 



80 

86A1 

86A2 

BOAS 

90C1 



14/- 
13/- 

IV- 

121- 
g- 

10/- 
8/- 

10/- 
26ZBGT 11/- 
28D7 71- 
29C1 20/- 
30A5 7/- 
30C1 7/6 
30C1S 11/- 
300] 7 13A 
30018 W- 
30 F5 111- 
30FL1 12/6 
30FL19 12/- 
30FL1I 12/- 
30L1 6/6 
301.15 12/6 
301.17 14/- 
30PI2 10/- 
80P18 14/- 
30PI.1 12/- 
30P1.13 12/- 
30PL14 12/- 
30PL16 12/- 
35A3 12/- 
36A6 11/- 
3505 6/8 



IB/-, 6072 

Sl-\< m:i 
S/- BH9.5 

57. fill"! 

8/- .6101 

26/- " ' ' ' 

8 6 6tjn 

S ' 8 S198 

.„, Bias 

"' 6136 
6140 
614G 
B159 

BIO 
6197 

6202 

18082 X S'; swe 

150C4 7/6 ;6 . (S „ 
180BTA18/-i M63 
2U 80/-| 6350 



100TH 60/- 
117N7GT 

30/- 
117I.7GT 

22/- 
117Z6GT 

10/- 



7/6 
8/- 
7/- 

10/- 
6/- 
6/- 
8/- 

10/- 
8/- 
9/6 
7/6 
7/6 
8/- 

10/- 
1/- 



POF87 13/- 
POF800 11/- 
PL'1'801 111- 
PCl'802 111- 
POF805 11/- 
POF806 13/- 
POMOSIB/- 
PCL80 12/- D26 
PCW1 9/- i I 7o 
POL82 8/- | 1 HH 
PCL83 8/6 U251 
PCI.84 8/6 I l"281 
PCL85 9/6 D8S9 
PCL86 9/6 1^301 
PCL8S 12/6 



TZ40 40/- 

U12/14 8/- 

017 8/- 

V 18/20 71- 

1-19 80/- 



w- 

B/- 

9/- 

8/- — 

5814A 10/- AZ41 71- ECCTH 10/- 

10/- LBL1 15/- Ell Ml 3/6 !•:•. 

30/- OBLS1 17/- BCC18918/- BY91 

30/-ICX83 9/- BOF80 8/- EZ35 8/6 , YClJiOl 12/- 

10/- CY31 71- ECFS2 7/6 EZ40 7/6 

5/- IH I 5/- ECF84 13/- EZ41 8/- 

7/6 -HA30 10/-IECF88 11/- EZS0 5/6 

12/-DA41 40/-! EOF80418/- BZ83 6/6 

7/- DAF91 4/6 EL'H21 10/- BZflO 41- 

18/- HM'92 6/- ECU:..", 12'- tW4/SM7h 

5/-IDA596 7/-IECH4S 9/6 I W4 ,so<,8/6 

15/- D096 8/- BOH81 6/6 Q810D 55/- 

7/6 l>FB2 10/- ECII1M 7/6 OB10H 40/- 

7/6 DI'H4 5/-IEC186 7/6 OTIC 10/- 

10/- IH'JB 7/- 1 KLI.-2 7/6 BTJ 15/- 

7/- DK97 Ul- BCM8 9/6 Q2380 8/- 

12/- UH63 6/-! ECI.S4 12/- OZ81 51- 

30/- l'HVV 5/8| ECl.s,; 9/6 QZS2 10/- 

12/-|DK;i2 8/-I EF.1B 5/- OS»* 10/- 



220PA 71- 
262B 30/- 
4 IBB 200/- 
7 16 A 80/- 



60/- 
9/- 



715B 

807 

811 

81.2A 

813 

81S 

829 

832 

868A 

872A 

884 

931A 

954 

955 

956 

U5SA 

059 

991 

11116 

1619 

MHO 

5517 

5612 

5654 

5670WA12/- 

6672 71- 



6922 
7044 
7199 
7044 
7551 



10/- 

9/- 

30/- 

27/6 

82/- 

10/- 

25/- 

8/- 

4/6 

807- 

4/- 

7/- 

30/- 

14/- 

10/- 

15/- 

10/- 

30/- 

22/6 



HK40 11/- 



DK'.'l 
DK92 
DK96 

DI.B3 
DM3 
DIM 

1 ) 1.92 

ni,93 

1)1.91 
DL95 

D1.9B 
II.MV0 



6/- 
9/- 
8/6 
8/- 
10/- 
8/- 
8/- 
4/- 
6/- 
6/6 
7/6 
5/B 



DM 160 10/- 

DTS0 7/- 

DY86 8/- 

DY87 9/- 

E80CC 20/- 

E88CC 14/- 

E!X)CC 12/- 

F.91H 8/- 

B93CO 7/- 

i: I -iii.i s/- 



»'- 7580 22/6 

Br VS'.ir. 22/6 

88/- 8013A 25/- 

W- 9001 4/- 

W- 9002 5/6 -- 
S0/-.9UOK B/- B186F 22/. 

20/- A18S0 20/- , BAM 2/- 

14/- AJ834 BO/- BASS 80/- 

35/- A20S7 17/B EABC80 71- 
15/- 'A2134 8/- F.AC91 4/- 

60/- A222B 18/- EAF* 



EF37A 8/- | HABCS0 8/- 

5/6 , HL2K 3/- 

9/6 HL23DD 

8/6 6/- 

8/- IIU1 4/- 

2/- HL92 6/6 

8/- HL133DD 

8/- 10/- 

5/6 HR2 12/- 

6/6 KF35 3/6 

8/- , KT2 6/- 

5/6 KT8C 20/- 

4/- KT32 8/- 

2/- , KT:«C 6/- 

6/- KT41 7/6 

KT44 6/- 

KT45 15/- 

KT63 6/- 

KT66 18/- 

K'C88 



PEN45 71- 
PBM46DD 

12/- 
PBN46 6/- 
PEX220A7/- 
PBN38310/- 
PEN384 71- 
PEN453DD 
10/6 
PENA4 7/6 
PEXDD 

4020 7/6 
PFL2O017/6 
PL30 10/- 
Pl/W 16/- 



6/- 
11/- 
11/- 

4/- 
11/6 
12/6 
13/- 
14/- 
12/- 

71- 
18/- 



EF39 
BF40 
El'-I I 
EF42 
EF50 
EF64 

BF6B 

BF80 

EF85 

BF86 

BP89 

BP91 

BFBS 

EF94 

EF95 

BK183 8/- 

Kl'lll 8/- 

EF-iil 21/- 

BFP60 10/- 

E1190 7/6 



V- 

31- 
2/- 
4/- 
8/- 
71- 
51- 
51- 

12/6 
6/- 

13/- 
8/- 



A22!l;l 16/- BB84 

AO/HL/DD IEB41 

8/-EB91 

AC/P4 41- BBC21 



EK.I2 
EI.2 
ELS 
E1.S2 
E1.35 
F.T.3B 
Bl . 
9/6 EL88 



AC/TH110/- BBC88 7/- 



AC2/I1L 9/- 
AC5/1'ES 

10/- 
AOj/PEN/ 

»D 8/- 
AC0/PEN6/- 
ARH 6/- 

ABP3 3/- 
ABP12 3/6 



EBC'41 8/6 

EBC'81 6/6 

l-:li,-f„.. 4/6 

EBC91 6/- 

BBF2 12/- 

EBF80 7/6 

EBF83 9/- 

EBF89 71- 

EBL1 14/- 



EI^Il 

|.;i,i2 

EL50 
ELS1 
EM 
EI.84 
BUS 
BUS 
F.L90 
EL91 
BL98 



6/- 
S/- 
10/- 

ti- 
ll. 

9/- 
17,1-, 

17/a 

9/6 
9/ 
6/- 
B/fl 

s;- 

51- 
8/- 
8> 
U- 

2/6 

«/- 



El,:|i|" 22/- 



PL81 
PL89 

PL83 
PL84 



PL302 14/- 
PL500 18/- 
PL801 10/- 
PP5/40010/- 
PT15 10/- 



PT83 

PY80 
PY81 
PY82 

nres 

PY88 



DABO80 5/6 
UAF49 9/- 
UB41 11/- 
D BC41 8/- 
UBOS1 87- 
CBF80 71- 
OBF89 7/6 
LISL21 11/- 
l.'C92 8/- 

ITCC84 10/- 
L'CCSS 71- 
UCF86 10/- 
UCH21 9/6 
UUH42 9/6 
I.'CH43 8/- 
OCH81 71- 
OOL89 8/6 
UCLS3 10/- 
UD143 12/6 
UF41 9/- 



UF42 
UF43 
TJF80 
UF85 
KP86 
L'F89 
ITL41 
UL84 
l'M4 



KTZ41 8/- 
LP2 71- 

MU4 6/- 
MH41 9/- 
MI^j 6/- 

MS/PEX 8/- 
MSPEXT 

10/- 
X7S 18/- 
NSP1 26/- 
NSP2 22/- 
OKP12 12/- 
ORP60 10/- 
PABC80 7/6 
PC86 12/- 
PC83 12/- 
l'L'97 9/8 
l'C-05 12/- 
PO900 12/- 
PG084 6/6 
PCC85 8/- 
EL821 6/- PCCSS 12/- 
ESI4 10/- I'l-CSfl 12/6 



9/6 
6/- 
6/6 

Off 

8/6 I UMS0 
PY80O 8/6 UUS 
PY801 8/8 I OU7 
PX25 10/- UU8 
PZ30 10/- I UC9 
QP3S 5/- 1"Y1N 



UY21 
UY41 
UYS2 
0X86 



9/- 
8/- 
8/- 
8/- 

111- 
7/6 
9/- 
6/6 

10/- 
71- 
81- 
8/- 

13/- 
7/- 
9/- 
9/- 
6/8 
6/6 
6/- 
3/8 
61- 
51- 
s:- 
■76 



QQVO3-10 

38/- 
QQVO3-20A 

100/- - 
QS92/10 3/6. VP23 
Q895/10 8/6 I VP41 
Q8108/45 VP210 

15/- VL'39 
Q81S0/15 8/-; VU111 
QV04-7 10/- VL-120 10/- 
QY3-12S W21 5/- 

160/- ' WS1M 6/- 
X65 5/6 

X66 8/- 

Wi'.M 7/8 
X78 20/- 
X*l M 18/- 
XC12 7/6 
XC15 4/6 
Z700U 4/- 
Z729 8/- 
Z759 23/- 
Z803TJ 15/- 



RIO 


12/- 


B17 


8/- 


K18 


7/8 


KLIS 


10/- 


8130 


12/8 


SP4 


5/- 


SP41 


bl- 


Sl'42 


8/- 


Sl'Bl 


41- 



SU2150A 10/- 
T41 12/6 



TBANSI8TOBS 

OC23 17/8 

OC24 82/6 

OC25 18/- 

OC26 8/- 

OC28 17/6 

OC29 17/6 

OC35 16/- 



OC36 
OC42 
OC44 
OC45 
OO70 
OC71 
OC72 
OC73 
Ui'Vfi 
0076 
0077 



15/- 
7/8 
6/- 
6/- 
6/- 
61- 
61- 

11/- 
61- 
61- 
61- 



OC78 61- 

OC78D 6/- 

OC81M 71- 
0081DH 71- 

OOS3 6/- 

OC139 12/- 

OC 1 40 16/- 

00141 85/- 
OO170 
Oi 171 
OO200 

OO202 15/- 

OC204 17/6 

OO205 20/- 

OO20B 22/6 

2X410 3/6 

2N412 3/6 

2N697 18/- 






23002 20/- 
23004 15/- 
28006 20/- 
AC128 8/- 
AF1I4 9/- 
AF115 71- 
AF116 8/- 
AF117 6/- 
AF118J 17/6 
CXT1 3/- 
GET114 5/6 
GET115 8/6 
GET11B12/- 
GET875 9/- 
GEI'--"10/- 
MAT101 8/6 
MAT121 8/8 
T1166 6/- 



GERMANIUM DIODES 



OA5 
OA8 

OA10 
OA70 
OA73 
OA79 



OA81 
OA85 
OA86 
OA90 
OA91 
OA95 



2/- 
8/- 
8/6 
21- 
2/8 
3/- 



CG4E 

CGIOK 

CG12B 

GKX23 
HEX 44 
GEX54 



SILICON BRIDGE CONHECTED POWEB 
RECTIFIERS, 100 P.I.V. 
1B20K10, 2 amps DC (1.4'xl.4*i6') 25/- 
LB4OK10, 4 ampa DC (1.4*xl.4"s.6* 30/- 
1B100K10. 10 ampa DC (g.gS*«2.25'xl') 85/- 



■!/6 
.],'.. 

B). 

:;/•• 

1/6 

2/3 

OAZ2WI WfaOAMM 8/-, OAZ213 6/6 VB10A8/- 
OAZ201 9/8iOAZ207 9/6 OAZ224 10/- 1EIIA - 
DAB9A9 6/-OAZ20S 8/- 'V 11425 6/6 VP.UA8/- 
OAZ203 7MOAZ810 6/- V11475 8/6 ZNBIWW 
OAZ204 6/8 0AZ211 5/8 'VP.D75 6/6, ZXB209/6 
OAZ205 6/-.OAZ212 7/61 VR7B 6/8 1 
8TC SILICON roHCTTON RECTIFIERS, 
HALF WAVE, 3 AMPS D.C. 
1IS310, 140 piv 4/- BS850, 700 piv ,16 

liSM-20, 280 piv 5/- 118360. 840 piv 8/- 

R3330. 420 piv 6/- K8370, 980 piv 9/- 

RS340. 560 piv 7/- BS380, 1120 piv 10/- 

FERRITE ROD AERIALS 

OSMOR PW/FRI .. .. ,v„ „" 8/8 ,i,a 

WEYRAD RA2W, with Car Aerial CoU 12/6 

FERP.ITE BODS OXLY. ',' dia. i 6' 1/9 each 

15/- per dozen. 



CATHODE RAY TUBES 

3GP1 — As recommended for P.E. Oscilloscope. 8" <!•»- 
screen; 6.3v lieatenu Mux. F.HT 1500v. 50/-; bSMll 
Tube Base 6/6. 

DG7-5, 2!" screen; EHT 800v,; 6.3v heaters. 56/-: 
B9G Tabd Base, 1/6. . 

40SA, li- screen, EHT 800v.; 4.0y heaters. Blue short 
pen rtenos coating suitable for photography, 60/-. 
B9 Tube Base. 1/6. 

JI-P7. 5' screen, yellow long persistence coating. 
Magnetic focussing and defection. EHT OOOOv. Except- 
ional brightness of the trace, 12/6. B14A Base, 8/6. 

SOB -CHASSIS EX TR 1934/5 AD3CBAFT TRANS- 
MITTER-RECEIVER 

1 Transmitter and Receiver Chassis (available in 100-125 
Mc/s or 124.0-145 MC/»), 15/-. 

2 I.F. Chaui* Type 478. 9.72 Mo/s. 15/- P-P. 5/- per 
oh. .--;?. 

These unit* are not in themselves complete and cannot 
be ined as complete transmitter or receiver. They are 
however, eminently suitable for use as sub-units in 
Aunillflers, Tuners, etc^ ^^^^^^^^^^^ 



April, 1966 



PRACTICAL WIRELESS 



Hi 



PRACTICAL 
WIRELESS 



blueprints 



Send (preferably) a postal order to cover the cost of the Blueprint (stamps over 6d. unacceptable) to 
PRACTICAL WIRELESS, Blueprint Dept., George Newnes, Ltd., Tower House, Southampton Street, 
London W.C.2. 



DOUBLE-FEATURE BLUEPRINTS 



The Strand Amplifier \ 

The PW Signal Generator / 

The Savoy VHF Tuner \ 

The Mayfair Pre-amplifier / 

The Berkeley Loudspeaker Enclosure \ 
The Luxembourg Tuner f 

The PW Troubadour 

The PW Everest Tuner 

The PW Britannic Two 

The PW Mercury Six 

Beginner's Short Wave Two ... 
S.W. Listener's Guide 

Beginner's 1 0-watt Transmitter 
Transmitting and Aerial Data... 

PW "Sixteen" Multirange Meter 
Test Meter Applications Chart 

The Celeste 7-transistor Portable Radio ' 
The Spinette Record Player . 

Transistor Radio Mains Unit "1 

7 Mc/s Transceiver f 



:::} 
:::} 
:::} 

dio\ 



SI- 
SI- 
S'- 
7'6 

61- 
SI- 

SI- 
SI- 

si. 
si. 



SINGLE-FEATURE BLUEPRINTS 

The Tutor 3'- 

The Citizen 5'- 

The PW Pocket Superhet 5'- 

The PW 35-watt Guitar Amplifier 5'- 

The Mini-amp 5'- 

The PT Multimeter 5'- 

The Beginner's Short Wave Superhet ... 5'- 

The Empire 7 Three-band Receiver 5'- 

Electronic Hawaiian Guitar 5'- 

Progressive Short Wave Superhet 5'- 



PLEASE NOTE that we can supply no blueprints other than those shown in the above list. Nor are 
we able to supply service sheets for commercial radio, TV or audio equipment. 



QUERY SERVICE 

The PW Query Service is designed primarily to 
answer queries on articles published in the magazine 
and to deal with problems which cannot easily be 
solved by reference to standard text books. In order 
to prevent unnecessary disappointment, prospective 
users of the service should note that: 

(a) We cannot undertake to design equipment or 
to supply wiring diagrams or circuits, to individual 
requirements. 

(b) We cannot undertake to supply detailed 
Information for converting war surplus equipment, 
or to supply circuitry. 

(c) It is usually impossible to supply information on 
imported domestic equipment owing to the lack of 
details available. 



(d) We regret we are unable to answer technical 
queries over the telephone. 

(e) It helps us if queries are clear and concise. 

(f) We cannot guarantee to answer any query 
not accompanied by the current query coupon 
and a stamped addressed envelope. 



QUERY COUPON 

This coupon is available until 7th April, 1966 
and must accompanyall queries in accordance with 
the rules of our Query Service. 

PRACTICAL WIRELESS, APRIL, 1966 



Published on tho 7th of each month by GEORGE NEWNES LIMITED. Tower House. Southampton Street. London, W.C.2, and printed 

ill Enpland oy V. A r.MOVGHS LIMITED. Idle. Bradford; and London. Solo Ascents for Australia and New Zealand: GORDON & GOTCH 

(Aysia) Ltd. So uth Africa: CENTRAL NEWS AGENCY LTD. Rhodesia. Malawi and Zambia: KINGSTON'S LTD. East Africa: 

STATIONERY & OFFICE SUPPLIES LTD. Subscription rate Including postage for one year: To any part of the World £1.3 0. 



PRACTICAL WIRE! ESS 



April, 1966 



16 PAGE TRANSISTOR LIST 1 , 

Send I', stamp for new list] 
all types of semi-conductors. 




NEW 1966 CATALOGUE 150 PAGES 

Fully detailed and illustrated components, equipment. 
Complete range of High Fidelity equipment in Stock. 
All types and makes. 5000 Stock lines. The Finest 
and largest Range available. A mine of information. 

Price 6'- post paid. 
CDCC with Catalogue. 6'- Discount vouchers gives 
2'- in pound discount on purchases. 

CATALOGUE COSTS NOTHING AFTER USING VOUCHERS 




(I) GLOBEM ASTER 

MWLW SW PORTABLE 

Full 3-waveband tuning. Pushbutton 
wavechange. Superhet printed circuit. 
Black-chromed cabinet II x 7} x 3±in. 
(SW 17-50 metres). Ear Record sockets. 
TOTAL COST /ft I Q A P -P- 
TO BUILD tO. IT.O 3 , 6 

* Building instructions on request. 



(6) VHF FM TUNER 

87,105 Me's Transistor Superhet. 
Geared tuning". Terrific quality and 
sensitivity. For valve or transistor 
amplifiers. < x3J x 2iin. 
TOTAL COST /_ |Q _ P.P. 
TO BUILD tO. IT.O 2 , 6 

(Cabinet Assembly 20'- extra) 
* Circuit and details on request. 



10 AND 20 WATT TRANSISTOR MONO AND STEREO HI-FI UNITS 



(3) PREAMPLIFIERS. 8 input 
selector. Treble, bass, volume, filter 
controls. l£mV to 300mV inputs. 
Battery operated or from Mains Unit. 
Output up to ISOmV RMS. 

MP2 Mono 9i x 2* x 2in. £5.10.0. p.p. 
2'6 (brown and gold front panel 8'6). 

SP4 Mono/Stereo. 9 x 3j x I6in., 
£(0. 19.6. p.p. 3'6 (front panel plate I2'6) 

* Detailed booklet on request. 

# ALL UNITS BUILT AND TESTED 
(9) MICROPHONES 



(2) POWER AMPLIFIERS. 10 watts 
RMS output. lOOmV input. 30os to 
20kc,s — IdB. 6 transistor. Push-pull. 
Panel sire 4 x 2j x I in. H S - 
TPAI0 3 3-S ohm spkr. £5.10.0, p.p. 2'6 
TPAI0 IS. 12-16 ohm spkr., 

£5.19.6, p.p. 2'6 
(Mains unit for I or 2 amplifiers, 
59'*, p.p. 2'6) 



The Finest High Fidelity at 
Unbeatable Prices 



(4) DEAC RECHARGE- 
ABLE CELLS 

Special offer at a fraction of 
normal price. Brand new 



#3.6 volt 500 
II" x lg" diam .... 



mA/H 
...I2'6 



• 9.6 volt 22S mA/H 
2-rV" x I" diam 20'- 



HI-FI 
WE CAN NOW 

SUPPLY FROM 
STOCK ALL MAKES 
OF HIGH FIDELITY 

EQUIPMENT 

Special Parcel 

Prices. Send list of 

requirements for 

quotation. 



•JC Professional 50K ohms 
Dm30l 79'6 

•sVSOk Stick Dm 1 07, 

Dynimic 69'* 

■«V 1 00c Xtal Stick 

with stand 32'* 

* BM3 Stick Mic. Xtal 47'6 



(5) BUILD A TAPE RECORDER 

Three speeds — 3 watts. 

Complete kits with new "363" decks. 

Supplied as preassembled sections. 

Complete with portable cabinets and 

Speaker — excellent quality. 

ic TWO TRACK * FOUR TRACK 

£26 & £30 8 P ; 6 P - 



(7) 5 WATT AMPLIFIER 

6-Transistor Push-pull. 3 ohms. 6mV 
into IK. 12 18V supply- 27 x 2 x l T in. 
BUILT AND TESTED 70/^ p - p - 

(optional mains units 64'- * '/** 2'- 
p.p. 2'-). Leaflets on request. 
New matching Preamplifier, 6 inputs, 
treble/bass/sejector volume controls. 6- 
lOmV o/put. 9-I8V supply. 79'6, p.p. V- 



(8) REGENT-6 

MW LW POCKET RADIO 

6-transistor superhet. Geared 
tuning. Push-pull output. Moulded 
cabinet S x 3 x l|in. Phone 
socket. Leaflet on request. 
TOTAL COST OC I P.P. 



TO BUILD 



2'- 





MULTIMETERS 


PT34 


1 k V ■ 39'* 


TP55 20k V £5.19.6 


Ml 


2k. V 49'* 


EP30k 30k V £6.10.0 


TPI0 


2k/V 75'- 


EP50k 50k, V £8.15.0 


EPIOk 


10k V 79'* 


500 30k V £8.17.6 


IT 1-2 


20k. V 89'* 


EPIOOk 100k V £10.10.0 


EP20k 


10k V 99'* 


See catalogue for details 



GARRARD DECKS — BRAND NEW FULLY GUARANTEED 



1000 mono £6 10 ATS «t--reo 18 6 

• •ait. £10 10 

. £8 19 8 ai"_'S mono 110 19 6 

M-o £7 10 8P&1 ntereo 111 10 

80001m stereo (8 19 a 8P2S Denun £13 19 8 



ATAOInucarvSU 10 
ino £11 19 8 
reo £U 19 6 

AT00 l>cnua £14 10 
■■*so»n«8S 



ATS mono S8 19 

til 10 
ATS Dcmm (11 19 6 
DeeeMlecMkIlll7 17 



(Ih QUALITY MW/LW 

V ' SUPERHET TUNER 

New printed circuit transistor design. 
Output for any valve or transistor 
amplifier. Full coverage with excellent 
sensitivity and selectivity. 9 volt 
operated. Complete with front panel 
etc. Size 6" x 2" x 4*. 
TOTAL COST 7Q 'A PP - 

TO BUILD 17V v . 



HENRY'S RADIO LTD. 

303 EDGWARE ROAD, LONDON W2 

PADdington 1008,9 

Open Mon. to Sat. 9-6. Thurs. I p.m. 

Open all day Saturday. 



(\Q) ROADSTER 

v ' MW LW CAR RADIO 

Supplied , as" Preassembled Panels. 
Permeability tuned superhet. Push- 
button wave-changer. Push-pull out- 
put. Fits any car.' 7 x 4 x 2in. 12 volt 

--th. Circuit on request. 
ASSEMBLY /ft I Q A pp - 

TOTAL COST tO. I T.O V6 
(Speaker, Baffle Car Fixing Kit. 20'-.) 



• LET US QUOTE FOR PARTS 
FOR YOUR CIRCUIT. SEND LIST OF 
PARTS FOR QUICK REPLY. MOST 
PARTS IN STOCK FOR ALL PUB- 
LISHED DESIGNS. LOWEST PRICES.